In the present study wound healing was examined in normal C57B1/6 male mice, diabetic mice, non-treated; and in diabetic mice treated with insulin. Small dermal wounds were made in the ears of the mice 40 h after the initial injection of insulin or vehicle alone. All animals were biopsied 8 h later. The wounds were examined by light and electron microscopy and wound components (capillaries, fibroblasts, PMN's oedema, collagen) were quantitated by lineal point analysis. The non-treated, diabetic mice demonstrated in inability to heal wounds when compared to controls; whereas, diabetic mice given a multidose insulin regimen demonstrated a response similar to controls. Insulin treatment of diabetic mice reduced the mean level of hyperglycaemia when compared to the non-treated diabetic mice. There was no detectable difference in the healing response with duration of diabetes in either the insulin-treated or non-treated diabetic mice. Although there was a mild reduction in hyperglycaemia, these data support the hypotheses that insulin is a necessary component of an adequate wound healing response.