36 patients from 19 families with erythropoietic protoporphyria were treated for about 5 years during the summer months with beta-carotene alone or beta-carotene plus canthaxanthin in daily doses of 50-200 mg. The effect of the treatment was evaluated clinically on the basis of information provided by the patients regarding the period of time they could stay in the sun. 18 patients became completely free of symptoms, 16 patients improved to some extent, and 2 patients noted a slight effect. Apart from the carotenaemia, no side-effects were recorded.