This report describes a nearly 25-year-old female with an interstitial deletion of band 14 in the long arm of one chromosome 6 (6q14). The deletion is contained within a de novo pericentric inversion with breakpoints in 6p11.2 and 6q15 (Karyotype 46,XX, del(6)(q13q15),inv(6)(p11.2q15). The distal breakpoint of the deletion and the pericentric inversion at 6q15 are the same, but the proximal breakpoints differ. Since cells with other chromosomal findings were not detected in cultured lymphocytes and fibroblasts, chromosome mosaicism seems unlikely. Thus, it is assumed that the inversion and the deletion originated from the same event. The development of a distinctive phenotype in the patient was observed over a period of 22 years. It includes characteristic dysmorphic facial features such as ocular hypertelorism, flat nasal bridge, prominent zygomatic bones, and a depressed glabella. A striking, non-progressive deficit of motor control is manifest in an inability to use her hands properly and a broad-based slow-motion-like gait. Although severely deficient in abstract mental abilities and speech development, she is well adapted to family life and to a school for retarded individuals. Normal height and head circumference, and reduced sensitivity to pain are noteworthy. Presumably the deletion caused the phenotype and the distinct behavioral pattern. This patient probably represents a novel chromosomal phenotype that results from aggregate haploinsufficiency of gene loci in the deleted region.