The information on membrane defects found in inherited disorders of platelet function is very limited. It has been presented here mainly in the form of a catalog of conditions in which membrane defects occur. Precise knowledge concerning the exact nature of the membrane defects is just beginning to appear in the literature. Most of the defects in abnormal platelets discussed are suspected, rather than clearly demonstrated. It is profoundly hoped that this presentation of current knowledge on the subject will stimulate the interest of investigators to pursue the subject further. New knowledge could lead to prevention or better treatment of the various conditions or help in the design of new approaches to the diagnosis and management of thrombosis.