We report the results over 15 years (1977-1991) for biochemical diagnoses of patients referred from throughout Italy and suspected of having a mucopolysaccharidosis. Of these, 147 patients were diagnosed as being homozygous or hemizygous for a specific lysosomal enzyme deficiency; 74 pregnancies at risk were monitored in their families; 76 heterozygote diagnoses were performed on their relatives, with a total of 48 positive diagnoses. We also report the analysis of genomic DNA from 11 unrelated Italian Hunter patients, using pc2S15 probe. DNA from two patients, digested with Pst-I, showed a variant pattern of hybridization caused by deletion or rearrangement of the gene.