For the past few years, two-dimensional diagnostic ultrasound methods have become available to veterinary medicine. In particular, linear-array real-time ultrasound would appear to be a very suitable diagnostic tool in the examination of the female genital organs of domestic mammals. The principles of this technique and the equipment available are described, and particular attention is paid to the method by which a diagnosis of pregnancy may be established in various animal species. In dogs and goats shaving will have to be done before the sound-transmitting/receiving transducer can be placed on the abdominal skin. This is not required in pigs and sheep, in which the skin of the inguinal area usually is bare. In mares and cows, the transducer can be introduced into the rectum, thereby minimizing the distance to the genital organs. Personal preliminary observations and the published experience reported by other investigators suggest that linear-array real-time ultrasound can be used: in (early) pregnancy diagnosis, early confirmation of non-pregnancy, prediction of the number of foetuses (mare, cow, sheep and goat), determination and quantification of embryonic/foetal mortality, to assess the viability of a foetus before/during parturition, to diagnose the possible presence of other foetuses on the completion of delivery (bitch, cat, sow), in the diagnosis of an enlarged, though non-pregnant, uterus and in the diagnosis of the ovaries. It can be expected that more quantitative information will come available for each of these uses within the next few years.