The amelioration of corticosteroid-impairment of healing by a stable gastric pentadecapeptide BPC-157 (GEPPPGKPADDAGLV, M(w) 1419, currently in early clinical trials for inflammatory bowel disease) was studied in thermally injured mice. Its effects on corticosteroid impaired healing of deep partial skin thickness burns, and burn-gastric lesions were investigated. Male NMRI-Hannover mice (sacrificed at 1-3,7,14 and 21 days following burning 20% of total burn area at the back (open flame for 7s) received intraperitoneally (per kg bw) 6alpha-methylprednisolone (Depo-medrol, 1.0 or 10.0mg), or an equal volume of saline (5.0 ml), once daily, first application 30 min after injury, last 24h before sacrifice. The injury was subsequently treated by topical application of a thin layer of pentadecapeptide BPC-157 cream at three different levels a neutral cream of no treatment. Pentadecapeptide BPC-157 consistently improved given burn healing (both microscopical and tensionmetry assessment), and counteracted corticosteroid-impairment of burn healing. In burn-gastric lesions investigation of the effects of BPC showed an anti-ulcer effect of its own in burned non-corticosteroid-treated mice and potentiated the anti-ulcer effect observed in 6alpha-methylprednisolone-treated mice. Pentadecapeptide BPC-157 inhibited corticosteroid immunosuppression. In vitro, in spleenic cells assessment, animals (sacrificed at day 21) treated with 6alpha-methylprednisolone 1mg showed decreased reactivity to nitrogen in comparison with control, healthy animals, while the addition of BPC-157 (1 microg/g cream) returned cell reactivity to values noted in control healthy animals.