The prevalence of congenital-nevus-like nevi (CNLN) in a group of 105 adults who had malignant melanoma (MM) was compared with that in a control group of 601 adults not afflicted by MM. Total cutaneous examinations were performed on both groups. The control group presented with complaints other than pigmented lesions. In this series, 10 (9.5%) of the group with MM had clinically diagnosed CNLN 1.5 cm or larger in diameter. These CNLN were not in contiguity with the MM sites. The 9.5% prevalence of CNLN in the group with MM was significantly higher (p less than 0.005) than the 2.5% CNLN observed in the control population. None of the patients in either group had large congenital nevocytic nevi (greater than or equal to 20 cm). In addition, in the group with MM, 5 patients (4.8%) had nevi spili (NS) and 13 (12.4%) had café-au-lait spots (CLS). The prevalence rates for these two types of pigmented lesions were not significantly different from those observed in the nonmelanoma control group (2.3% for NS; 13.8% for CLS). The relative risk for developing MM is 4.1 in people with CNLN compared with those without CNLN, which indicates that these nevi may be markers for individuals prone to develop malignant melanoma.