Pseudoporphyria, a cutaneous disorder characterized by skin fragility, vesiculation, and scarring, has been reported as a side effect of naproxen therapy in children with juvenile rheumatoid arthritis (JRA). We report the results of a 6-month prospective study to determine the prevalence of pseudoporphyria in our JRA population. All the patients with pseudoporphyria had received naproxen for > or = 4 weeks at the time of the study. Of the patients treated with naproxen, 12% (9/74) developed this complication. No patient had significant elevation of free erythrocyte protoporphyrin, excluding the diagnosis of true erythropoietic protoporphyria. We conclude that pseudoporphyria is a common side effect of naproxen therapy in children with JRA, even in geographic areas without high sun exposure. Because of the risk of facial scarring with pseudoporphyria, physicians and parents of children with JRA should be aware of this complication.