The effect of basic fibroblast growth factor (bFGF) on angiogenesis and granulation tissue formation in normal and healing-impaired animals was studied. bFGF showed a dose-dependent enhancement of granulation tissue formation in the subcutaneous implantation of a paper disk in normal rats. Application of bFGF restored the formation in healing-impaired rat models treated with steroid, chemotherapy and X-ray irradiation. The angiogenic activity of bFGF was also demonstrated in the micro-pocket assay using the cornea of rabbits. Repeated applications of bFGF accelerated closure of full-thickness excisional wounds in diabetic mice, but the high doses showed rather diminished response. In contrast histological and gross evaluation of wound tissues revealed enhanced angiogenesis and granulation tissue formation in a dose-dependent manner. The findings suggested that the topical application of excess amounts of bFGF might reduce its ability to promote wound closure because of the prolonged responses in both neovascular and granulation tissue formation.