In a non-selected population of 809 office employees (454 women and 355 men) 81 persons were diagnosed as having rosacea, giving a prevalence of 10% (women 14%, men 5%). The rosacea group was compared with the rest of the study population. Most of the cases were rather mild. The rosacea was of an erythematotelangiectatic type in 81% of the cases and of a papulopustular type in 19%. Unilateral lesions were found in 11 subjects (14%). Only 17% of those with rosacea were impaired by sunlight, whereas 26% improved. In the rosacea group, 27% were found to suffer from migraine and 42% from a tendency to flush, compared with 13% (p less than 0.001) and 16% (p less than 0.001) respectively in the comparison group. Flushing and the regulatory mechanism of the blood vessels thus seem to be of importance in the pathogenesis of rosacea. Individuals with good pigmentation ability showed a tendency to a decreased occurrence of rosacea. The frequency of eye complaints was the same in the two groups.