Double minutes are considered the products of DNA amplification and are rare in normal human cells. They have been observed in cultured lymphocytes in selected samples of human populations as one of the characteristics of the so-called rogue cells. We scored 9500 metaphases of cultured lymphocytes from 65 subjects with a variety of heredity and sporadic tumors and from 30 healthy subjects. The 15 cells with double minutes were found in subjects with multiple endocrine neoplasia type 1 (14 cases) and with familial adenomatous polyposis (1 case). Only one rogue cell was found among the 15 cells with double minutes.