An adult male patient with a "de novo" pure trisomy 1q32---q42 was studied. Literature review of 33 cases with 1q trisomy allowed singling out a distinctive phenotype by eliminating clinical features of concomitant aneusomies. It is concluded, however, that the clinical pictures of the "pure" and "impure" 1q trisomies are similar and that the critical segment includes bands q32 and q41.