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The Cayenne's headlights and grille work closely to resemble those on the 911 and Boxster and identify it as a Porsche.

As it is with the 911 Turbo, the Cayenne Turbo models are distinguished by larger grilles that increase the amount of air flowing through the engine bay. The Porsche Cayenne Turbo S is further distinguished by quad tailpipes, body-color front grilles, and special badging.

The designers believe they've transferred all the emotion of a Porsche sports car to the Cayenne, but we'll leave that call to you. The designer's handiwork has produced a 0.38 coefficient of drag, impressive for a big SUV, and good for limiting wind noise at high speed.

The Cayenne is not a small vehicle. Measuring 188.2 inches in length, with a wheelbase of 112.4 inches, it's longer than the BMW X5 and and about the same as the 2006 Mercedes-Benz M-Class and a few hundred pounds heavier than either. Conversely, at 4,762 pounds in its lightest specification, the Cayenne weighs 550 pounds less than a Lincoln Navigator, which is two feet longer. An inspection underneath this SUV suggests that it's perhaps over-engineered compared to many mass-market sport-utilities, but Porsche engineers preferred not to take chances with their first SUV in the event that some owners actually drive it aggressively off road.

In size, the Porsche Cayenne most closely matches Volkswagen's Touareg, which is no surprise given the two vehicles were developed jointly by Porsche and VW. Engines and other Cayenne components are built by Porsche in Zuffenhausen, Germany, and mated to the Cayenne at an assembly plant in Leipzig. Both Cayenne and Touareg were created from the same basic blueprint. The standard Cayenne even shares its V6 engine with the Touareg. Engine and suspension tuning, styling, and all the finish work were the separate responsibility of each manufacturer.

This auto-industry backgrounder is relevant to any consumer preparing to part with a substantial amount of money for a high-end SUV, because if two vehicles share a foundation, they're likely to share a basic quality, or lack thereof. Porsche insists the Cayenne is uniquely Porsche, and as reviewers we can vouch for that. We can also tell you a loaded VW Touareg sells for about 40 percent of the price of a high-end Cayenne, and the choice is worth considering. Meanwhile, Audi has launched its own version of this vehicle, called the Q7.

Porsche's SUV has near optimal front/rear weight distribution of 52 / 48 percent, for outstanding handling balance in all circumstances (the weight in most unladen SUVs is more heavily biased toward the front). At least as important, in Porsche's view, is the Cayenne's optimal aerodynamic balance. Aerodynamic downforce on the rear wheels increases with speed, delivering the high-speed stability that has become a Porsche trademark.

We prefer the monster (though expensive) 20-inch wheels, too. And if money were no object we'd choose both of the appearance packages: The SportDesign Package adds more prominent, aero-tweaked side sills and a larger rear spoiler, and it gives the Cayenne a more powerful, aggressive appearance. The Black Monochrome Exterior Package finishes the roof pillars, window trim and molding in black, giving the windows a dark, monolithic look.

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Anyone who has spent time in one of Porsche's sports cars will get a familiar feeling in the Cayenne driver's seat. The cues are pure Porsche: the shape and feel of the gear selector or the thick, grippy, steering-wheel; the three-spoke hub design, with a brand crest and multiple controls for audio, trip computer, and climate adjustments; the ignition switch to the left of the steering column or the contour of the seats.

The Porsche Cayenne's instrument cluster is tucked under a single, prominent arch, with two big gauges on either side of a central multifunction display, tachometer on the left, speedometer on the right. This display presents information on audio and trip functions, mechanical operations, and ambient conditions. Automatic speed and wiper controls are located on stalks on either side of the steering column. The bulk of the switches, including audio and climate controls, are racked in the center of the dash above the center console. These are replaced with a CRT monitor on Cayennes equipped with Porsche Communications Management. A dozen vents throughout the cabin distribute warm or cool air evenly.

The Cayenne is not as richly appointed as a similarly priced Range Rover, but it's not supposed to be. The emphasis here is sporting flair rather than traditional luxury. With the exception of a cheesy looking headliner and oddly designed armrests in the doors, the materials and finish are acceptable for a vehicle of this ilk. One of our test vehicles was equipped with the Light Wood package. It's polished to a gloss and expensive looking, but almost blond.

The standard leather upholstery is high grade, while the standard metal trim has a brushed finish. The front seats stand out for their balance of support, comfort, and adjustment range, and the navigation display screen is one of the largest we've encountered.

The navigation system calculates routes and makes adjustments very quickly. It uses DVDs rather than CDs, allowing for maps for the entire United States on a single disc, rather than several that must be changed from region to region. There's also an optional electronic logbook, which automatically records the mileage, journey length, date and time, starting point, and destination address for every trip made. In addition, buyers can opt for a module that will help you find your way back to your starting point, even if the roads or trails aren't on the system's map.

The Porsche Cayenne transports five adults in reasonable comfort. The rear seat is well contoured, with excellent headroom and decent legroom, even when the front seats are well back in their travel range. Seating for five is something we haven't seen previously in a Porsche, but don't expect the interior volume of a Lincoln Navigator, and don't look for a third-row seat.

The rear seatback folds forward in a 60/40 split, and it includes a pass-though slot with a ski sack, allowing the Cayenne to haul longer, narrow items inside without flattening (or messing up) the rear seat. A cargo net keeps grocery bags and other items from sliding around during travel and a retractable shade-type cover opens and closes over the cargo hold.

The Porsche Cayenne boasts 19 cubic feet of stowage space with the rear seat in place and 62.5 cubic feet with the seat folded. That gives the Porsche more cargo space than the BMW X5 but about 10 cubic feet less than the 2006 Mercedes-Benz M-Class. The tailgate is two-stage, so either the glass or entire gate can be opened upward, and the electronic latch lets you simply lower the gate to the latch while the electric mechanism pulls it shut.

The dimensions of the tailgate opening and load floor allow the Porsche Cayenne to haul small appliances such as a bar-size refrigerator or a large TV set. Moreover, with an impressive payload of 1,600 pounds, a Cayenne owner should be able to haul just about anything that can be crammed inside and on top without worrying about exceeding recommended weights.