The microscopic examination of semen provides clinically important information. However, this information has been limited by the low resolution of the light microscope. Scanning electron microscopy (SEM) permits observation of free cells and has been used to study the spermatozoa of rabbit (Dott, 1969; Hafez & Kanagawa, 1973), bull and ram (Dott, 1969), monkey (Hafez & Kanagawa, 1973), man (Fujita, Miyoshi & Tokunaga, 1970; Hafez & Kanagawa, 1973; Martin & Gould, 1975), and other mammalian species (Zaneveld, Gould, Humphreys & Williams, 1971). In the present study equine spermatozoa were examined by scanning electron microscopy.