Albino rabbits were treated four or six times daily with 1% prednisolone acetate, 1% medroxyprogesterone acetate, or a control vehicle, after one of three conditions. First, after 3-mm linear perforating stromal incisions; drugs were given for seven days, and wound bursting strength was determined. Prednisolone suppressed wound tensile strength by 20%; medroxyprogesterone suppressed it by 11%. Second, after trephination, drug administration for 14 days decreased collagen formation in the scar buttons by 43% in the prednisolone-treated group and 39% in the medroxy-progesterone-treated group. Third, after thermal burns; when drug application followed the burn immediately, deep ulceration or perforation developed in 85% of the controls, in none of the prednisolone-treated group, and in 17% of the medroxyprogesterone-treated group. When drug delivery was withheld until day 6, severe ulceration developed in 44% of both groups. In both experiments, stromal neovascularization was markedly suppressed by prednisolone, but only moderately decreased by medroxyprogesterone.