The purpose of this experiment was to trace the development of animals treated with exogenous corticosterone in order to determine whether maturation progressed more slowly but in a continuous fashion or whether the animals experienced a temporary cessation of development (`pubertal diapause’) during the prepubertal period. Daily administration of corticosterone in the drinking water (160 µg/mJ 4% ethanol in tap water: B-treated) from 22 days of age produced a significant delay in both vaginal opening and ovulation while 4% ethanol (the vehicle for B) or 16 µg B in ethanol was compatible with normal puberty. At 32 days of age, body weights, ovarian and uterine weights were comparable in controls, ethanol-treated and B-treated rats but adrenal weights were depressed by 160 µg B. Puberty progressed normally in ethanol-treated and 16 µg B-treated rats and organ weights were comparable in these groups on days 36 and 40. At these times, all organ weights in rats treated with 160 µ% B remained at levels comparable to day 32. A significant increase in organ weight took place only at puberty onset around 45 days of age. In contrast to other groups, puberty was not associated with adrenal growth in 160 µg B-treated rats. Estradiol, progesterone and prolactin levels remained level and similar to values found on day 32 in 160 µg B-treated rats until they entered puberty. No significant differences in FSH and LH were found among the groups. It can be concluded that rats maintained on a high dose of corticosterone passed through a waiting period during which very little growth or increased steroid secretion occurred and that they escaped from this ‘pubertal diapause’ as puberty began, despite the absence of recovery of adre