A system is described for controllably ventilating garments such as protective suits and jackets, especially garments which are worn by the occupants or operators of moving vehicles such as motorcycles, bicycles and some aircraft. Vents are provided in the front of the garment for controllably admitting air into the garment by means of flaps or other devices which cover the vents and which can incrementally be removed to control the amount of air entering the garment. Additional vents are provided at the back and sides of the garment to allow the exiting of air and prevent billowing of the garment due to air being trapped inside. The various vents which are provided in the garment are covered with air permeable material such as mesh which advantageously is stretchable to provide greater flexibility to the garment both while it is being worn and to facilitate putting on and taking off. The ventilation system of the invention can be used in conjunction with garments of various configurations and materials including leathers, woven fabrics and waterproof material.