Oestrogen, progesterone and androgen inhibit uterine cell death after the depletion of oestrogen. In the present study, we investigated effects of glucocorticoid on death of mouse uterine cells. Castrated female mice were given a daily injection of 17 beta-oestradiol (0.2 microgram/mouse/day) for 3 days, and then an injection of 5'-[125I]iodo-2'-deoxyuridine ([125I]IdUrd) to label DNAs of uterine cells with 125I. Mice were killed at intervals during subsequent treatments, and the retention of [125I]IdUrd incorporated into the whole uterus was determined. On subsequent injection of vehicle only, the 125I-radioactivity retained in the whole uterus rapidly decreased. Injections of dexamethasone (50 micrograms/mouse/day) reduced the loss of 125I-radioactivity slightly but significantly. Dexamethasone also showed synergistic effects on the retention of 125I-radioactivity when it was daily injected together with 17 beta-oestradiol, progesterone or 5 alpha-dihydrotestosterone. The present results suggest that glucocorticoid may affect the processes involved in the uterine cell death, in a manner such as inhibiting the uterine cell death or delaying the removal of DNAs of dead cells from the uterus.