The mechanism of spermatozoal degeneration in male genital tract obstruction was evaluated. Epididymal fine-needle aspiration was performed in 17 azoospermic men with distal obstruction of the genital tract, but in whom testicular cytology revealed adequate spermatogenesis. From the contents of each puncture, smears with May-Grunwald-Giemsa and Papanicolaou staining were prepared. All indigenous epididymal cytologic types were identified in the smears. In aspirates which contained spermatozoa, large cells with foamy cytoplasm and round or kidney-shaped nuclei were also found. In some of these foam cells heads of mature spermatozoa were engulfed within the cytoplasm. It is suggested that in male genital tract obstruction, the role of the foam cells within the epididymis may be to phagocytize and disintegrate the trapped spermatozoa. The cellular origin of these foam cells is probably the epithelial lining layer of the epididymis itself.