The photoprotective effect of peroral β-carotene medication was evaluated on 66 patients suffering from polymorphous light eruptions. With a dosage of 75 mg/day, 51 of the patients responded favourably, as judged clinically. 55 of the patients noted that their threshold tolerance to sunlight was elevated during β-carotene treatment, in some patients even with a factor of 20–30. The average increase in sun tolerance was with a factor of about 8. The therapeutic effect of β-carotene was dose-dependent. Some degree of sun exposure seemed to be necessary for the photoprotective effect to evolve optimally. The photoprotection gradually became evident in a couple of weeks. Upon stopping medication the patients original sun sensitivity recurred in 2–30 days. Side-effects of the treatment were mostly negl