Long-wavelength ultraviolet A (340-400 nm UVA1) phototherapy has been reported to be effective in atopic dermatitis, localized scleroderma and other T-cell-derived skin diseases. UVA1 as an adjunct to systemic immunosuppressive treatment was found to be safe, and effective in 10 patients with chronic cutaneous (seven lichenoid and three sclerodermoid) graft-versus-host disease (GVHD) after stem cell transplantation. Complete and partial responses were achieved in six (60%), and in three (30%) patients, respectively. One patient had improvement of sclerotic skin lesions. At a median follow-up of 14 months, two patients with lichenoid lesions relapsed. Both responded to another treatment cycle. Furthermore, we treated seven patients with UVA1 as primary therapy for acute cutaneous GVHD grades II and III in a pilot experience. Five patients had a complete response with no relapse at a median follow-up of 9 months after UVA1. Two patients showed no response and systemic steroids had to be started. UVA1 therapy is feasible, well tolerated and can be effective in treating chronic as well as acute GVHD confined to the skin thereby avoiding systemic steroids. Our results should be confirmed in larger studies and the effectiveness of UVA1 compared to other established treatment modalities.