Background: The presence of multiple atypical nevi or numerous melanocytic nevi increases the risk for the development of cutaneous melanoma. Objective: We sought to describe a distinct clinical phenotype characterized by numerous (>100), small (≤4 mm), darkly pigmented melanocytic nevi that are uniform in color. Methods: Biopsy specimens from 6 patients (3 men and 3 women; age range, 44 to 81 years) with this clinical phenotype were reviewed and compared with a database of melanocytic lesions analyzed by the Yale Dermatopathology Laboratory (YDL) in the year 2000. Results: Of the 6 patients, 4 had multiple primary melanomas develop (n = 2-4), ranging from in situ to 1.0 mm in depth. The other 2 patients each had 1 nevus with severe cytologic atypia. When compared with the YDL database, our patients were more likely to have the following pigmented lesions: junctional melanocytic nevi, junctional lentiginous nevi, junctional nevi with cytologic atypia, and simple lentigines (P < .001). Conclusions: The longitudinal evaluation of patients with this phenotype can be challenging because similar-appearing pigmented lesions (small and uniformly dark-brown to black) had a range of histologic diagnoses from simple lentigo to junctional lentiginous nevus to thin melanoma. (J Am Acad Dermatol 2003;48:707-13.)