The analysis of ultrastructural, kinetic and immunological characters of spermatozoa aspirated from the proximal segments of the epididymis of patients with congenital absence of vas deferens showed that most of them are defective. These spermatozoa, utilized in different procedures of assisted reproduction, showed a reduced fertilization rate. The data obtained in this study seem to indicate that CAV affects the development and functional properties of epididymal spermatozoa.
