Abstract: A crankcase ventilation system for motor vehicles comprises a main ventilation system and a safety ventilation system, in which at an air guiding housing of the intake system, connecting pieces are arranged to which the lines of the two systems are connected. So that the connection between the lines of the two systems and the air guiding housing is simplified with respect to construction and also requires little space, a joint connecting piece having connecting pipe sections for the lines of both systems is provided at the air guiding housing. Separate ducts lead away from the connecting pipe sections and extend to remotely arranged outlet openings. The outlet openings of both ducts--seen in flow direction--extend at a distance from one another.