The incidence of leukocytospermia (> 1 million white blood cells/ml semen) and concentrations of white blood cell populations in semen from men whose partners experience unexplained recurrent spontaneous abortion by conventional testing criteria are described and compared to those of men whose partners have normal reproductive histories. Comparable seminal granulocyte and total white blood cell concentrations between groups suggest that couples with unexplained recurrent abortion do not have an abnormally high incidence of subclinical genital tract infections for which leukocytospermia could serve as a marker. However, a significantly higher prevalence of elevated CD4+ and CD8+ T lymphocyte concentrations in semen from men whose partners have cellular immunity to sperm antigens (i.e. produce embryotoxic factors in response to sperm antigen stimulation) warrants further investigation.