A patient with hydrops fetalis caused by beta-glucuronidase deficiency was found to be homozygous for a C to T transition at nucleotide position 672 in his cDNA. Genomic analysis showed the presence of pseudogenes for the beta-glucuronidase gene. After separation of PCR products of the gene and the pseudogenes it was shown that the patient and his father were heterozygous for the C-T 672 transition and the mother did not carry the mutation.