Ultraviolet irradiation provokes the development of new melanocytic naevi, or changes in existing naevi, leading to repeated surgery of atypical naevi and becoming a continual burden for individuals with many of these lesions. To determine the influence of long-term medication with the radical scavenger beta-carotene on newly developing atypical naevi, a single-centre, randomized, placebo-controlled study, prospective over 3 years, was started double-blind in 62 patients with numerous clinically atypical naevi. Beta-carotene (25 mg) was given twice daily for 36 months in the treatment group (n = 30) and saccharose capsules as placebo in the control group (n = 32). The total number of newly developed naevi in the beta-carotene group (n = 18) was 68 versus 88 in the placebo group (n=21) (not significant). Of 12 different locations on the human body evaluated separately, only in two, the lower arm (p = 0.03) and the feet (p = 0.03), was there a difference for the beta-carotene group in the quantification of naevi. Overall, it is concluded that beta-carotene does not reduce the development of new naevi in patients with numerous atypical naevi.