The aim of this study was to determine if transrectal colour Doppler sonography of uterine arteries is a useful method to quantify uterine changes during the first 12 weeks after parturition in cows. Examinations were carried out on days 1, 7, 14, 28, 56 and 86 after parturition (day 0) in 42 Holstein-Friesian multiparous dairy cows (mean lactation number: 2.63+/-0.73). Findings obtained by transrectal manual palpation were quantified using scores for uterine size (SUS) graded from 1 to 6. The mean diameter of intrauterine fluid accumulation within the uterine body and the presence of a dominant follicle and/or a corpus luteum were examined using B-mode sonography. Blood flow was measured by determining blood flow volume (BFV) and pulsatility index (PI) of the uterine arteries. Clinical uterine involution was complete on day 28 as demonstrated by transrectal palpation and B-mode sonography. BFV declined (P<0.05) steeply between days 1 and 7 from 4312 ml/min to 1443 ml/min and moderately (P<0.05) to 230 ml/min on day 28. From this time on there were no significant changes (P>0.05) of BFV until the end of the study. The pulsatility index rose from 1.54 on day 1 reaching a peak value of 5.56 on day 28 and decreased (P<0.05) linearly to 3.13 on day 86. The results show that transrectal colour Doppler sonography is an additional tool for examining uterine changes during the first 12 weeks after parturition in cows. While uterine blood flow changes were only demonstrated during the first 4 weeks of the puerperium, the pulsatility index was also suitable to investigate alterations in uterine perfusion during the next 8 weeks after parturition.