Disturbances of acrosomal development and function significantly impair the fertilizing capacity of spermatozoa. Therefore, evaluation of acrosomal morphology and function is of particular importance in the diagnostic testing of male infertility. Acrosomal disturbances include either specific defects showing a complete absence of certain acrosomal structures or various acrosomal malformations in combination with nuclear or flagellar defects which indicate acquired testicular disorders. As examples of specific acrosomal defects, the syndrome of round-headed spermatozoa (globozoospermia), the crater defect syndrome and the syndrome of decapitated spermatozoa are discussed. In addition to disturbances of acrosomal morphology, the assessment of acrosomal proteinase activity and the acrosome reaction as a method of evaluating impaired acrosomal functions is discussed. Clinical examples demonstrate the importance of these sperm function tests in the fertility testing of infertile men.