The effects of an irradiation 6 times the minimal erythemal dose of UVB were studied using a visual scale from 1 to 4+ in 12 patients aged under 45 years with a past medical history of basal cell carcinoma, and in 12 sex-, age- and skin-type-matched controls. Erythema was significantly more intense at days 15 (p less than 0.01) and 22 (p less than 0.001) in patients than in controls. Pigmentation was significantly weaker at day 22 than in controls (p less than 0.005).