Cytogenetic and dermatoglyphic studies were performed on a group of 197 institutionalized patients with severe mental and physical handicaps in order to evaluate the contribution of chromosomal aberrations on the etiology of the condition, and to determine whether any association exists between the dermatoglyphics and the severe handicaps. There were 4 patients with trisomy 21 and 2 patients with a de novo balanced reciprocal translocation. In addition, 9 patients were found to have a pericentric inversion of chromosome 9 (inv (9) (p11q13)). Other chromosome variations identified included inv (1) (p11q11) (one case), elongation of 1 qh (one case), and telocentric chromosome 13 (two cases). Dermatoglyphics from the patients excluding cases with Down syndrome were compared with those from 500 normal controls. Significant differences were observed in several dermatoglyphic characteristics, including simian crease, fingertip pattern, mean a-b ridge count, thenar/first interdigital pattern, hypothenar pattern, and hallucal pattern. The present study indicated that de novo balanced translocation as well as chromosome duplication or deficiency is causally related to the severe combined handicaps. This study also showed that the incidence of inv (9) (p11q13) in the patients was 4.2 times higher than that in the general Japanese population. If a real association exists between the inv (9) (p11q13) and severe handicaps, the increase of inv (9) (p11q13) in the patients may be explained by the concept of a risk factor. Moreover, the dermatoglyphic deviations found in patients may be evidence that pathological factors had been operating during early embryonic life in some of them.