The aim of this study was to examine the effect of long-term treatment with glucocorticoids on the uterine response to oestradiol. Ovariectomized rats were treated with crystal triamcinolone acetonide (0.1 mg/100 g, i.m.) or saline (0.1 ml/100 g i.m.) for 29 days. Over this period five injections were administered, one per week. On the second day after the last triamcinolone injection, rats were treated with a single injection of oestradiol dipropionate (5 micrograms/100 g, s.c.) or vehicle (olive oil, 0.1 ml/100 g, s.c.). The effects of oestradiol in the uterus were determined by measuring mitotic index, bromodeoxyuridine (BrdU)-labelling index (BrdU was injected 2 h before the rats were killed; 2 mg/100 g, i.p.), and proliferating cell nuclear antigen (PCNA)-labelling index 24, 36 and 48 h after the injection of oestradiol or vehicle. Long-term treatment with glucocorticoids resulted in dissimilar changes in oestradiol-induced proliferation in epithelial and connective-tissue (stroma) components of the uterus. In luminal and glandular epithelia, there was an initial reduction in proliferation at 24 h, followed by an increase at 36 h and a further reduction at 48 h after the oestradiol injection. In stromal cells of the endometrium, triamcinolone treatment caused a large constant increase in oestradiol-induced proliferation throughout the experiment. The glucocorticoid treatment had no effect on the parameters without oestradiol administration.