To investigate the influence of topical application of insulin on the formation of basement membrane (BM) in rats with deep partial thickness scald. Ninety-six SD rats were inflicted with deep partial thickness scald on the back and were randomized into A group (n = 48, with subcutaneous injection of 2 ml of isotonic saline on the 1 post scald day (PSD)) and B group (n = 48, with subcutaneous injection of 0.1 U of insulin and 2 ml of isotonic saline on the 1 PSD). The rats received the treatment every other day until wound re-epithelization completed. Then the rats were sacrificed on 2, 3, 4, 5, 6, 10, 14 PSD, and on the day when the wound re-epithelialized completely. The skin samples of 1 cm in width were harvested at the edge of the wound for reticular fiber staining and for morphological observation of the wound BM with transmission electron microscope. The expression of laminin-5 mRNA and laminin in keratinocyte was determined by RT-PCR and Western blotting, respectively. Integrated and continuous structure of the basement membrane was observed in B group. Laminin-5 mRNA expression was much higher in B group than that in A group on 10 and 14 PSD (P < 0.05 or P < 0.01). Laminin-5 mRNA expression was decreased in both groups when epithelialization completed. But the Laminin-5 protein expression on 14 PSD and the day of epithelization (56 +/- 8, 101 +/- 13) was obviously higher in B group than that in A group (39 +/- 5, 73 +/- 16), (P < 0.05). Subcutaneous injection of 0.1 U insulin beneath the scald wound is beneficial to the acceleration of the wound re-epithelialization process, and to the improvement of the wound healing quality.