The invention is based on a known rollover protection system for motor vehicles having two seat-related rotary bars permanently articulated to the vehicle body, said rotary bars each being fixable in the stored resting position by means of a holding device, and being rotatable into a locked support position by means of a sensor-controlled drive. To compactly design the system with several functional parts, the invention provides a toggle lever arrangement to convert the movement of the drive into a rotary bar movement, said arrangement being articulated to the drive and the rotary bar such that it is folded at least partially within the area framed by the rotary bar when the rotary bar is in its resting position.