BACKGROUND UVA1 phototherapy has recently demonstrated high levels of efficacy and tolerability for treating a variety of inflammatory and neoplastic skin diseases. OBJECTIVE The purpose of the present study was to assess the clinical efficacy of UVA1 (340~400 nm) phototherapy for treating pityriasis rosea and to assess the course of the disease after treatment. METHODS Fifteen patients with extensive pityriasis rosea were treated with low-dose UVA1 phototherapy (starting at 10~20 J/cm(2) and then it was increased to 30 J/cm(2)). The treatments were given 2~3 times a week until complete clearance of lesions was achieved or until there was partial improvement without further amelioration, in spite of 5 additional treatments. The rate of clearing was monitored by estimating the pityriasis rosea severity (PRSS) score and the pruritus score. RESULTS The extent of disease (PRSS) in all 15 patients lessened during the study (30.1+/-3.6 vs. 2.0+/-1.6, respectively, p<0.05). The overall reduction of the PRSS showed a significant improvement after the second or third treatment. The pruritus of 12 of 15 patients lessened during the treatment period, and it was unchanged in the remaining 3 patients. The mean previous duration of disease was 11.2+/-4.9 days and this did not interfere with the successful outcome of UVA1 phototherapy. CONCLUSIONS This study shows that UVA1 phototherapy is a useful, well-tolerated treatment option for patients suffering from pityriasis rosea with extensive eruptions and considerable pruritus.