Objective To study the testicular ultrastructure in CBAVD patients. Methods Ultrastructure of testicular tissue was studied in 13 CBAVD patients with azospermia whereas the testicular morphology under light microscopy was normal. Results The presence of thickening,multilayered,finger shaped protuberent to seminiferous tubules in variable degrees in basement membrane was confirmed at ultrastructural level in 13 CBAVD patients.Collagen fibres revealed an increase in number,proliferation,disturbance in variable degrees and no polarity in all the 13.Malformed heads,metachromatic granules nuclei with abundant bulla,full or partial absence of middle mitochondria sheath were seen in most of spermatozoa.Of 5 cases,invagination and low electronic density layered materials were presented in acrosome and acrosomal cyst respectively.Most of sertoli cells presented abundant lipid droplets and degradative bodies in their cytoplasm in all cases.In 2 cases,tight junctions between sertoli cells were not found. Conclusions Microstructural alteration of testicular tissue,especially conspicuous in spermatozoa and in the limiting lamina of testis,might be a contributory cause of azospermia in addition to the clinical absence of vas deferens.