The aim of this study was to evaluate sperm morphology (teratozoospermia) and its effect on xenogenic human sperm-hamster oocyte penetration assay (HOPA). Sperm morphology assessment was performed in 140 infertile patients and 25 healthy individuals. According to Kruger's strict criteria teratozoospermia was diagnosed in 38 individuals out of 140 infertile males. HOPA assay was performed for 20 teratozoospermic patients and 10 healthy volunteers. No significant decrease in HOPA values was observed in cases of isolated teratozoospermia. The sperm anomaly severely influencing HOPA values was asthenozoospermia. We believe that evaluation of sperm morphology according to the strict criteria of Kruger should be applied for routine andrological practice which reflects rapidly changing 'normal' values of human semen.