We describe the prenatal diagnosis of a fetus at risk for mucopolysaccharidosis (MPS) Type IVA (Morquio syndrome) using enzyme analysis of chorionic villus tissue. The family had two previous affected children, one with progressive nonimmune hydrops fetalis presenting at 16 weeks gestation and one mildly affected 5 year old. The parents had decreased levels of N-acetyl galactosamine-6-sulphate sulphatase in cultured skin fibroblasts indicating that carrier detection is possible for Morquio A syndrome.