A male patient, who had intra-uterine growth retardation, a low birth weight and hypotonia due to a chromosome 2q33.1 deletion, is described. At the age of 20 years, he displays short stature, microcephaly, a high forehead, microstomia, large teeth and is hypertonic. He is severely mentally retarded, has not developed speech, is hyperactive, anxious and at times aggressive. Full tiling array showed a de novo 14 Mb deletion at chromosome region 2q32.3q33.2, further delineating the 2q33.1 microdeletion syndrome.