With the aim of investigating the influence of trisomy 21 on the expression of heritable morphological features, we recorded the palmar and plantar dermatoglyphic patterns in 48 children with Down syndrome (DS), in both their parents, and, as a control, in 57 of their siblings. Using the Kendall tau rank correlation test, a considerable parental influence on the frequency of true patterns in the interdigital areas (IDA) III and IV of the palms (P = 0.3%) and soles (P = 1.0% and 3.8%, respectively) is demonstrated for the control siblings. In the children with DS, this influence is discernible as well, although with no statistical significance. A greater number of families may be required to settle the question.