Objective: To determine possible relationships between number of leukocytes, function of seminal vesicles, and seminal quality. Design: The study was carried out on men who consecutively attended an infertility clinic between June 1989 to June 1991. Setting: This study was conducted in a private immunological center for infertility, a tertiary care center, The Centro Inmunologico-Seccion Esterilidad y Reproduccion. Patients: Semen samples from 280 infertility patients attending an Immunological Center for Infertility were analyzed. Main Outcome Measure: We evaluated the effect of leukocytospermia in the presence of normal or abnormal function of seminal vesicles on seminal quality. Results: Sperm count, percent of motile sperm, and percent of sperm vitality were significantly reduced when both leukocytospermia and hypofunction of seminal vesicles were present (P < 0.01). Leukocytospermic subjects with normal function of seminal vesicles showed similar seminal parameters to those nonleukocytospermics. The incidence of subjects with antisperm antibodies measured by direct immunobeads was significantly higher in leukocytospermic men with hypofunction of seminal vesicles. No differences in the incidence of antisperm antibodies with nonleukocytospermic samples were observed in those with both leukocytospermia and normal function of seminal vesicles. Conclusions: These data provide evidence that white blood cells were deleterious for seminal quality when seminal vesicles were also affected.