Transforming growth factor α (TGFα) is a keratinocyte-growth-stimulating factor which may have a role in epidermal hyperproliferation, psoriasis, and wound healing. Since increased epidermal proliferation occurs in response to UV radiation, we have measured the amount of TGFα in exudates from normal and UVB-irradiated human skin. Cutaneous exudates were obtained using the skin chamber abrasion technique from one side of the back of volunteers (n = 10) with normal skin (collected following skin contact times of 2 and 30 min). Exudates were similarly obtained from the contralateral side of the back at sites irradiated 2 h previously with 3 × the minimum erythemal dose UVB. Levels of TGFα were measured by radioimmunoassay. Normal human skin released TGFα immediately after abrasion: unirradiated, 63 ± 18 ng/ml; irradiated, 89 ± 15 ng/ml. Levels of TGFα increased within 30 min to 110 ± 14 ng/ml in unirradiated skin and to 190 ± 17 ng/ml in irradiated skin. Irradiated sites at 30-min time points were significantly higher (p < 0.05) than all other samples. The presence of releasable TGFα in normal skin suggests a role for TGFα in wound repair mechanisms.