We estimated the prevalence of persons with histologic dysplasia in at least one of two nevi examined by biopsy to be 53% in Utah's caucasians. This apparently high prevalence indicates that such lesions may represent a normal variant of a melanocytic nevus, perhaps those in the process of active proliferation. Regardless of the apparent ubiquity of these lesions, examination of biopsy specimens led to a grading scheme of histologic dysplasia that may reflect chronologic stages in the neoplastic development of melanocytic nevi. Comparison of these histologic findings with the clinical examination yielded the unexpected result that dysplasia and lesion size are independent of each other. Lesions 3 mm in diameter or smaller were as likely to be dysplastic as those much larger. There was, however, a statistically significant relationship between histologic dysplasia of a nevus examined by biopsy and the person's total number of melanocytic lesions. This finding indicates that the pathology grading scheme may be useful. The high prevalence of dysplastic nevi dilutes the clinical significance of a dysplastic nevus as an isolated finding and thereby lessens the importance of pathologic findings in the diagnosis of dysplastic nervus syndrome.