Long-wavelength UVA (340-400 nm UVA-1) phototherapy has been reported to be effective in atopic dermatitis, localized scleroderma and T-cell-derived skin diseases. We retrospectively investigated 70 patients with acute cutaneous GVHD after allogeneic haematopoietic cell transplantation or donor lymphocyte infusion. Complete and partial responses with a median duration of 10 months were achieved in 49 (70%) and 17 (24.3%) patients, respectively. Overall, 47 (67.1%) patients were not treated with systemic steroids. Furthermore, immunosuppression could be tapered in 24 (34.3%) patients while they were receiving UVA-1 treatment. Responses were seen irrespective of age or type of conditioning. Treatment was very well tolerated. After a median follow-up of 18 (range 10-60) months, three patients developed epithelial skin neoplasia. We conclude that UVA-1 therapy is feasible, well tolerated and can be an effective treatment for acute GVHD of the skin, thereby avoiding the use of systemic steroids and/or allowing a more rapid tapering of systemic immunosuppression in a substantial number of patients. The results of this retrospective analysis warrant larger, prospective studies and the effectiveness of UVA-1 therapy should be compared with other established treatment modalities.