ABSTRACT.From 1976 to 1984, there were 149 Down's syndrome live births in Western Australia. Where previously the coexistence of congenital heart disease was a major determinant of early mortality, current survival rates do not reflect this. Survival rates have significantly increased over the last decade: particularly so for those with coexistent congenital heart disease. Projected frequencies for Down's syndrome persons in Western Australia are expected to significantly increase. This rise in prevalence will have major economic effects on the planning and delivery of health care for this population.