We have used oral psoralen photochemotherapy (PUVA) to treat four patients with chronic graft-versus-host disease of the skin, oral mucosa, and liver, who had responded only partially to long-term immunosuppressive therapy (prednisolone, cyclosporine, azathioprine). PUVA therapy was delivered to the entire skin but not to the oral mucosa, and immunosuppressive therapy was continued in all patients. Two patients' skin lesions improved considerably; the oral lesions healed and did not recur in one. Immunosuppressive therapy could be reduced in these two patients. One patient with sicca signs did not improve. One patient had to interrupt PUVA therapy because of side effects attributed to 8-methoxypsoralen (nausea and vomiting). No flare of acute cutaneous graft-versus-host disease was noted during PUVA therapy. Chronic graft-versus-host disease of the liver did not improve in any patient.