Finger and palm prints of 220 Cuban mongols, all trisomic 21, were statistically compared with those of a group of 400 normal Cuban individuals. The most important dermatoglyphic findings in the patients were: an excess of ulnar loops on the 2nd and 3rd fingers, and radial loops on the 4th and 5th fingers; a paucity of patterns in the thenar/I area; more hypothenar true patterns, specially ulnar loops, higher percentages of patterns in the II and III interdigital spaces with less true patterns in the IV interdigital space; distal position t" of the axial triradius and large atd angles of more than 70 degrees; high values of the main-line index; predominance of radial type of the C line and higher frequencies of type 11 of the D line. The simian crease, especially the complete variety, had more diagnostic value than the Sydney line. Parathenar patterns which did not seem to have been described previously in mongols, were significantly more frequent in the patients than in controls. The results are very similar to those observed in other countries and it seems that the peculiar dermatoglyphic pattern of patients with Down syndrome is not affected by ethnic influences.