The effects of nicotinamide on the microvasculature and wound healing were examined in rats subjected to thermal injury. Rats (250 g) were treated with 50 mg nicotinamide intraperitoneally twice daily for 21 days and then heart and brain biopsies were taken. Skin biopsies were removed from sites in and adjacent to the injury throughout the course of healing. Tissues were stained for alkaline phosphatase and capillary length density was determined by morphometric analysis. Significant increases were observed in the heart, brain, and dermal tissue of treated animals compared to controls. Capillary density in the injured skin was significantly greater when compared to the injured skin of saline-treated controls. The injuries of the rats that were treated systemically with nicotinamide healed significantly faster than saline-treated as determined by planimetric evaluation of the granulation bed and eschar.