The beneficial effect of sunburn-spectrum ultraviolet (UVB) phototherapy on uremic pruritus was studied. Seven patients were treated twice weekly for 4 weeks with UVB to one half of the body and placebo phototherapy to the other half. All patients noted generalized improvement without localization of benefit to the UVB side, suggesting a systemic effect of UVB. A comparison of three schedules varying from one to three treatments weekly showed that the percentage of patients responding was not influenced by frequency of UVB exposure, although patients treated more intensively improved faster. In three patients, improvement was delayed until 2 weeks after completion of a course of six treatments over 2 weeks, indicating a delayed onset of benefit in at least some patients. Overall 32 of 38 patients improved after a course of six or eight UVB exposures. Pruritus has recurred in 15 patients after a mean remission of 3 months. Sixteen patients are known to remain in remission for a mean of at least 10.6 months after the first or second course of treatment. The present evidence indicates a systemic mechanism of action for the long-lasting relief of uremic pruritus afforded by UVB phototherapy.