Semen was collected from all the mature Reindeer bulls (9) in the Glenmore herd, both normal and vasectomized. Nineteen samples of semen were obtained. Reindeer semen is a viscous fluid, generally amber in colour: after vasectomy its viscosity is much lower. The mean volume of the ejaculates was 0–5 ml. and mean sperm density 467 × 104 spermatozoa. Motility was low in comparison with other mammals and the proportion of eosinophilic spermatozoa was high (74.5%). Other determinations included measurements of the size of unstained spermatozoa, and of fructose and citric acid concentration in the semen.