Wellcome Institute of Comparative Physiology, The Zoological Society of London, Regent's Park, London NW1 4RY, U.K. Interest in the application of the techniques of artificial breeding to non-domesticated mammals has been stimulated in recent years by the failure of some species to breed in captivity and by the decreasing availability of animals from the wild. Several authors have drawn attention to the need to develop techniques suitable for exotic animals (Jones, 1971;Francoeur, 1972; Rowlands, 1965,1974; Warner, Martin & Keeling, 1974), but as yet very few species have been studied. A brindled gnu (Connochaetes taurinus) at The Zoological Society of London was sedated with Xylazine (Rompun, Bayer U.K. Ltd) and semen was collected by electroejaculation using finger ring electrodes and a sine wave stimulator (Watson & Hime, 1976). Stimulation for periods of 5 sec with 5-sec rest periods was commenced with a frequency of 10-15 Hz and a peak voltage of