Objective of the study was to record, by means of ultrasonographic examination, changes occurring during lactogenesis in the udder of healthy ewes and of ewes with pregnancy toxaemia. The work was carried out in 28 ewes, 16 with pregnancy toxaemia (group A) and 12 healthy controls (group B). B-mode and Doppler ultrasonographic examination of the udder of ewes was performed. During the last month of pregnancy, grey-scale intensity values of mammary parenchyma in group A were significantly greater than in group B (P = 0·007), as was also the progressive increase in grey-scale intensity values in both groups (P < 0·001). Blood mammary input was significantly greater in ewes of group B than in ewes of group A (P < 0·05), as was also the progressive increase in blood input in both groups (P < 0·001). Further, differences between the two groups were identified in pulsatility index (P = 0·007) and in mean blood velocity (P = 0·036), but only during the last fortnight of pregnancy. After lambing, grey-scale values decreased sharply compared to those in pregnancy (P < 0·01), whilst blood input, pulsatility index and mean blood velocity continued the same trend as at the last stage of pregnancy, with differences between the two groups still prevalent (P < 0·05). There was a reverse correlation between grey-scale intensity values and milk quantities (P < 0·035) and a correlation between blood input and milk quantities (P < 0·07). The progressive increase in the diameter of the external pudendal artery was significant (P < 0·001), but no significant differences were evident between the two groups (P > 0·35). Differences between group A and group B in all other haemodynamic parameters studied were not significant, neither throughout the last month of pregnancy (P > 0·25), nor during the first week of lactation (P > 0·06). However, their progressive changes during the last month of pregnancy were significant (P < 0·02).