Since the introduction of the Mercedes-Benz M-Class in 1998, many other premium-brand automakers have thrown their hats into the luxury SUV ring. To remain in the hunt, Mercedes has made constant improvements to its midsize SUV, increasing the feature content and performance, updating its looks and addressing the build quality issues that plagued early models.

Even so, the M-Class was falling behind amidst better-handling and better-dressed car-based SUVs. Finally, after eight years using the same platform, Mercedes readied the truck's successor. The 2006 Mercedes-Benz ML350 and ML500 are more powerful, better-handling and loaded with upscale features. Six inches longer overall, the new M-Class rides on a 4-inch-longer wheelbase and is 2 inches wider, though its storage area has been cut to 72.4 cubic feet when the 60/40-split rear seat is folded down. Instead, the extra inches go to the passenger cabin, where occupants enjoy added leg- and shoulder room. Despite the increase in dimensions, a third-row seat is no longer an option, as the all-new R-Class wagon has been designated for the family crowd.

An improvement over the previous body-on-frame design, the 2006 Mercedes-Benz M-Class is built on a unibody chassis that's stiffer, lighter and better able to deliver Mercedes-like ride quality. Stretched longer and wider, yet with less ground clearance than the old ML, the ML350 also has a more aggressive stance. The ML350 is powered by a 3.5-liter V6 with 268 horsepower. The ML500 still uses a 5.0-liter V8, but horsepower is bumped from 288 to 302. Both engines use a seven-speed automatic transmission that sends the power through a permanent four-wheel-drive system.

The design of the cabin isn't radically different than before, but it has an open, airy feel that the old M-Class lacked, and materials quality is much improved with large helpings of wood and aluminum trim. One of the most noticeable changes is the lack of a console-mounted shifter, replaced by a small stalk on the steering column to make room for American-size cupholders. The original M-Class caught a wave of opportunity that lasted longer than even Mercedes could have ever expected. Even though there are now many worthy vehicles in the premium SUV segment, the new Benz's combination of cutting-edge safety features, commendable on-road performance and plentiful creature comforts keep this pioneering luxury SUV right up there with the best in the class.

The Mercedes-Benz M-Class is a five-passenger SUV available in one of two models, ML350 and ML500. The standard ML350 comes standard with full-time four-wheel-drive, 17-inch alloy wheels, automatic climate control, power-adjustable front seats and a bare-bones four-speaker CD stereo. The ML500 gets 18-inch wheels, speed-sensitive steering, privacy glass, more deluxe Multi-Contour seats with heaters, multizone climate control, a leather interior, walnut trim, and additional chrome detailing. Among the numerous options are active bi-xenon headlamps, 19-inch wheels, a Harman Kardon Logic7 sound system with glovebox-mounted CD changer, a DVD-based navigation system, a rear-seat entertainment system, Keyless Go and a sunroof. An off-road package includes a two-speed transfer case, differential locks and a height-adjustable air suspension.

The ML350 comes with a 3.5-liter V6 rated for 268 horsepower. The ML500 uses last year's 5.0-liter V8, but power increases from 288 hp to 302 hp. Both engines use a seven-speed automatic transmission that sends the power through a permanent four-wheel-drive system. The standard 4WD system is intended mainly for winter use; off-road enthusiasts can get low-range gearing by ordering the optional off-road package.

Standard safety features include traction and stability control, four-wheel antilock disc brakes, side-impact bags for torso protection and two full-length head curtains. The PreSafe system is optional and adds additional protection in the event of a collision. If the onboard computer determines a collision is imminent, PreSafe can pull the front seatbelts taut, adjust the seats to optimal positions and even close the sunroof to prevent ejection during a rollover. The ML's performance in NHTSA crash testing was impressive, as the Benz posted perfect (five star) scores in both frontal- and side-impact testing, while scoring a still respectable four stars for rollover resistance.

From behind the wheel, the 2006 Mercedes-Benz M-Class feels lighter on its feet than the original, yet just as stable. With the optional air-spring suspension, the ride quality is plush and responsive. Throw the new ML into a corner and it rolls moderately, understeers predictably and sticks longer than you'd expect. On the road, the ML350 possesses plenty of passing power, but feels a bit shy on torque from a stop. If you want more punch off the line, spring for the V8-powered ML500, which sends 302 hp through the same seven-speed transmission.

There's plenty of room for 6-footers up front and all ML500s come standard with multicontour seats that provide excellent support; ML350s offer them as an option. The Mercedes-Benz M-Class has a tasteful, modern look that doesn't sacrifice functionality. Materials quality is generally very good, and the overall layout is open and airy. Maximum cargo capacity is 72.4 cubic feet, which is less space than the old M-Class offered. Most families will find the SUV plenty roomy, though the heavy rear liftgate will make you want to splurge on the power opener.