The mean survival in Trisomy-13-syndrome patients is reported to be 130 days. We have diagnosed 21 cases of this syndrome in this institution (11 females and 10 males); 15 patients had regular trisomy 13 and 6 had translocation-trisomy 13 karyotypes. The mean survival of the 19 patients who died was 97.05 days; translocation patients survived longer than regular trisomy patients. The oldest living patients with trisomy 13 are a girl 19 and a boy 11 years old. Both are black, have regular trisomy 13 karyotypes and have had most of the manifestations of the syndrome. No mosaicism was detected in repeated cytogenetic studies. The 19-year-old patient is the oldest known living person with regular trisomy 13.