Complete semen analyses including computer-assisted sperm motility and morphology assessments were performed to determine if semen and sperm differed between HIV-seropositive men and fertile controls, or differed with symptoms, or CD4+ peripheral cell count categories. Previous studies included small numbers of men and presented conflicting conclusions. Two hundred and fifty non-vasectomized HIV-seropositive men and 38 fertile controls each provided one semen sample. Non-parameteric statistics were used to analyse both continuous and nominal data. Fertile men had significantly greater semen volume, sperm concentration, percent motility, percent rapid and linear motility and total strictly normal spermatozoa than HIV seropositive men. Neither total number nor subtypes of leukocytes in semen differed between the two groups. Among the HIV seropositive men, significant differences in semen analyses were found between CD4+ cell count, clinical, and AIDS categories. Lower CD4+ cell counts (< 200 mm-3) were associated with significantly lower percent motility, percent normal sperm morphology by strict criteria, significantly more spermatids in semen, and higher percentages of teratozoospermia, oligoasthenoteratozoospermia and leukocytospermia. Healthier men, based on clinical categories, had significantly more normal shaped spermatozoa and fewer had azoospermia, oligoasthenoteratozoospermia or leukocytospermia. Many HIV-seropositive men have normal semen analyses, but as the disease progresses more defects are found, particularly in strict criteria sperm morphology.