After a two-day period of instruction in the use of a linear real-time ultrasonic scanning machine the results obtained by three operators scanning a variety of types of ewe under different conditions were recorded and compared with the actual lambing results. In the first season an overall accuracy of 95 per cent was achieved for the diagnosis of barren ewes and ewes carrying either one or two or more lambs. However, monitoring the accuracy achieved for the diagnosis of zero, one, two, three or four lambs demonstrated an improvement in expertise with time, the accuracy increasing from below 70 per cent to over 90 per cent. A particular improvement was observed after a comparative session with an experienced operator. Analysis of the figures of accuracy for zero, one, two, three and four lambs highlighted the differences between operators which were less evident if only the results for zero, one or two or more lambs were analysed. These analyses showed that 'newly trained' operators were not at first able to scan successfully. However, after a period of acquaintance with the technique (approximately 500 ewes) and an 'appraisal session' with an expert the accuracy of the operators improved sufficiently to be of commercial value to hill flocks and possibly to low-ground flocks with limited housing.