An all-terrain vehicle (ATV) includes a frame and a pair of front and rear wheels suspended from the frame. A straddle-type seat has a main portion and a secondary portion to accommodate a driver and a passenger. The wheelbase of the ATV is increased in length (compared to conventional ATVs) so as to increase stability and comfort for the driver, and/or to accommodate a passenger behind the driver. The passenger and secondary seat portion are disposed in front of the rear wheel axis and moved closer to the center of the wheelbase. Moreover, the combined center or gravity of the ATV, rider, and passenger is moved closer to the center of the wheelbase to improve stability, comfort and/or safety. The driver and passenger each have sufficient space to actively position themselves without significantly interfering with each other.