We describe 9 patients who presented Becker's nevus (BN) together with a malignant melanoma (MM). Eight patients were male. In 5 patients the MM was on the same body site as the BN. The melanoma was of the superficial-spreading type in 7 cases and in 1 patient was within the BN. Twice a dysplastic-nevus syndrome was diagnosed and in 2 patients a familial melanoma. To the best of our knowledge this is the first report of the co-occurrence of BN and MM.