A 3 MHz ultrasonic transducer was used to make pregnancy diagnoses in 320 milk and beef cows and heifers, on average 41 days after the last insemination. The ultrasound diagnostic findings were systematically confirmed by rectal palpation. Signs of pregnancy were detected as early as the 25th day after insemination. Discounting 16 doubtful results, the accuracy of positive diagnosis (94 per cent) was better than negative diagnosis (89.7 per cent). Ultrasound scanning could be used for the study of embryo mortality or for the determination of fetal age.