This study assessed the condition of spermatozoa from the proximal vas deferens of men after vasectomy. The fluids of both proximal vas deferens were collected from 67 vasectomized men by cannulating the vas deferens at the time of vasectomy reversal. Selected sperm parameters were analysed after incubation of the spermatozoa for 30 min at 37 degrees C. Sperm concentration in the proximal vas from vasectomized men (16,312 +/- 21,496 million per ml, geometric mean: 7948 +/- 398 million per ml) was significantly higher than that of fertile men and was maintained at a constant level independent of the duration of vas obstruction. The means of sperm motility (36.2 +/- 26.2%), spermatozoa with normal morphology (50.7 +/- 21.7%), sperm viability (53.0 +/- 25.3%) and hypo-osmotic swelling test (HOS-test, 53.9 +/- 21.7%) were statistically lower than the respective values for normal fertile men. There was no significant correlation between the duration of vas obstruction and the above semen parameters. In 46.4% of vas fluids all spermatozoa were immotile and this condition was more common after 3 years of vasectomy. Immotile spermatozoa in the proximal vas fluids at the time of vasectomy reversal may be an important factor for predicting semen quality and fertilizing ability after vasovasostomy. There were no significant differences in the results of sperm-cervical mucus penetration test (CMPT) between spermatozoa from vasectomized and fertile men. Antisperm antibodies on the surface of spermatozoa from the vas of vasectomized men were determined by the immunobead test (IBT; 78.6% for IgG, 32.1% for IgA) and sperm cervical mucus contact test (SCMC, 36.4%).(ABSTRACT TRUNCATED AT 250 WORDS)