The aim of this study was to assess the effect of human immunodeficiency virus (HIV), hepatitis C (HCV) and B (HBV) virus infection on semen parameters. Semen samples were obtained from 27 HCV, 34 HIV, 30 HBV and 41 HCV-HIV-seropositive patients and compared with those of a control population of healthy seronegative subjects. Tests for detection of HIV, HCV and HBV were performed on seminal samples. The sperm concentration was significantly decreased in HCV- and HBV-seropositive males compared to that of controls (P < 0.001). The mean sperm motility (a + b) was significantly decreased in HCV- and HBV-seropositive (P < 0.001) and in HCV-HIV-seropositive subjects (P < 0.05) compared to that of controls. The sperm viability was significantly lower in HCV- and HBV-seropositive men than in controls (P < 0.001). The normal morphology was significantly reduced in HCV-seropositive and HBV-seropositive men (P < 0.05) with respect to that of controls (P < 0.05). The sperm concentration after sperm wash was significantly higher in controls than in HCV-, HIV-, HBV- and HIV-HCV-seropositive men (P < 0.001). We can conclude that HBV- and HCV-infected men have a significantly impaired sperm quality compared with that of controls. The reason for the better sperm quality in our series of HIV- and HCV-HIV-infected men is still under debate. Further investigations in a larger case series are warranted.