Applications of atomic force microscopy to ultrastructural investigation of human spermatozoa are �discussed, with particular emphasis to their most common pathological alterations, which are recognized to be associated with male infertility. Morphological alterations can be located in the head, neck piece, and/or in the flagellum. The consequences of these defects on infertility-related topics are examined in the light of aberrations caused in varicocele and in other spermatozoa morphological alterations like globozoospermia, oligoasthenospermia, and in semen from patients with HIV syndrome. Special attention is given to the temperature effects on sperm abnormalities. The application of the present approach to pharmacology, namely, the development of male contraceptive methods, is also referred.