This chapter is intended to provide an accurate visual description of normal and abnormal bovine sperm morphology as seen under the light microscope. The photographs were taken × 1000 magnification and enlarged × 1.6, unless specified otherwise, using either a) differential interference microscopy (DIC), b) phase contrast microscopy, c) eosin-nigrosin-stained sperm smears, or d) Feulgen stained smears as indicated in the legends. When viewed with a critical eye, there is an extremely wide variation in form and structure within the various categories of sperm cell abnormalities. It would be an impossible and fruitless task to attempt to show every minor variation in appearance of each type. Therefore, a series of photographs has been put together showing the main features of each type of abnormality so that any other deviation observed can easily be recognized as to the category in which it belongs. The nomenclature applied to the various abnormalities is that preferred by us, although generally accepted by other workers. Synonymous nomenclature used by other workers is included in the discussion on interpretation of sperm cell abnormalities in Chapter 5 .