A new design of a simple plastic microvascular clamp is described. This consists of two jaws and an elastic ring which fits into special recesses in the jaws and provides full closing pressure. Changes in the dimensions and material of the ring permit the closing pressure to be varied. The clamp is designed for once-only use in microsurgery; this obviates the difficult and time-consuming cleaning and sterilization required with metal clamps. Experimental trials on animals have shown the clamp to be reliable, with traumatization of the vascular wall kept to a minimum.