The impact of demographic factors on the prenatal diagnosis and elective termination of Down syndrome in Hawaii between 1987 and 1996 were examined. Data were obtained from a population-based birth defects registry and included 306 Down syndrome cases. 131 (43 per cent) of the cases were prenatally diagnosed. Of the prenatally diagnosed cases, 110(84 per cent) were electively terminated. Advanced maternal age or having a maternal serum alpha-fetoprotein screen performed increased the probability of having an affected pregnancy prenatally diagnosed and electively terminated. Far East Asians were substantially more likely to have an affected pregnancy prenatally diagnosed and electively terminated. Pacific Islanders and Filipinos were less likely to have cases prenatally diagnosed and electively terminated. Prenatally diagnosed and electively terminated Down syndrome cases had disproportionately fewer additional birth defects than live births or fetal demises, suggesting that for many of the electively terminated cases additional birth defects may not have been identified. This implies that the elective termination of Down syndrome-affected pregnancies may influence not only the Down syndrome prevalence but also that of other birth defects.