Different forms of ultraviolet radiation have been used in the management of PITYRIASIS ROSEA. In the following study, UVA and UVB radiation were compared in a right LEFT comparative trial. Twenty patients showing pityriasis rosea were included. The patients were divided into two groups a and B. both groups received UVA to the right side of the body. To the left side of the body, group A was exposed to broad band UVB (BB UVB), 311nm. To study the pathological changes, skin biopsies were taken from both sides before treatment and after partial remission of the lesions. In all cases, clearance of the lesions was obtained on both sides within 3-5 weeks. However, resolution was always earlier on the UVB side than the UVA side. As regards the UVB side, clearance of the lesions was obtained at the end of three weeks in group A receiving BB compared to the fifth week in group B receiving UVB 311nm. Cumulative doses needed to achieve cure were significantly lower in group A. when the UVA side was compared in both groups, it was found that group A cleared faster than group B which might suggest A systemic effect of the UVB rays that initiated cure of the disease followed by resolution of both sides. Pathological findings correlated with the clinical results. We could therefore conclude that both BBUVB and NBUVB 311nm are useful in the treatment of PITYRIASIS ROSEA. BB UVB could be recommended as it achieves a faster response needing a smaller cumulative dose. The assessment of the therapeutic efficacy of UVA in this disease requires studying its use alone in a separate study. The mechanism of action of phototherapy in the treatment ROSEA is not clear, an immunomodulatory effect could be suggested and requires further studies