Intrauterine luminal fluid in diestrous mares has been associated with uterine inflammation. The objectives of this study were to measure the incidence of intrauterine luminal fluid in anovulatory mares, and to determine the association of uterine fluid with uterine and oviductal inflammation. Intrauterine luminal fluid was detected ultrasonographically in 18.8% (19101) of anovulatory mares. Thirteen anovulatory mares with uterine fluid and 10 anovulatory mares without uterine fluid were subsequently re-examined, and their uteri and oviducts were evaluated histologically for inflammation. Only 43.5% (1023) of the mares maintained a fluid (410) or non fluid (613) condition at their second examination, indicating that intrauterine luminal fluid occurred dynamically in these anovulatory mares. Moderate to severe uterine inflammation was not related with the detection of uterine fluid. A greater incidence of moderate to severe uterine inflammation was not detected in mares with 2 detections of fluid in contrast to mares with 1 or no detections of fluid. Regardless of the occurrence of uterine fluid or the amount of uterine inflammation, oviductal inflammation was minimal in the anovulatory mares.