A subtle terminal deletion of the short arm of chromosome 8 with a breakpoint in p23.1 was detected in amniocytes. Parental chromosome studies revealed a similar deletion in the father. The fetus did not have any abnormalities in a level II ultrasound. The pregnancy was continued and resulted in the birth of a baby girl. The child was normal at six months of age and no heart murmur was detected. In a retrospective review of cases in our laboratory, four other cases with a deletion del(8)(p23.1) were found. Three were paediatric cases with microcephaly, developmental delay, ASD, VSD, pulmonic stenosis, congenital and behavioural abnormalities. One was a 29-year-old woman with a mosaic karyotype. She had a history of spontaneous abortions and no known cardiac defect. Using conventional cytogenetics and/or FISH studies with 8p telomere probe and 8 painting probe, the 8p23.1 deletions were shown to be either terminal or interstitial. The karyotype from the prenatal case was compared with the other cases of 8p23.1 deletions in our laboratory to see if there was a discernible difference in the size of the deletion. The deletion in the proband seemed to involve a more distal 8p23.1 breakpoint. In the father's high resolution chromosomes (550-850 band level) the breakpoint appeared to be 8p23.1 approximately 23.2 and FISH studies using an 8p telomeric probe confirmed a terminal deletion. Interstitial deletion of sub-band 8p23.1 was associated with phenotypic abnormalities and distal 8p23.2pter deletion was found in apparently normal individuals, therefore, 8p23.1 appears to be the critical region for clinical abnormalities.