Gaucher disease (GD) is caused by a deficiency of -glucocerebrosidase activity mainly due to mutations in the gene coding for the enzyme. More than 100 mutations have been identified to date and their frequencies have been established in several populations, including Ashkenazi Jews, among whom the disease is particularly prevalent. In order to study the molecular pathology of the disease in patients from Argentina, we conducted a systematic search for mutations in the glucocerebrosidase gene. Genomic DNA from 31 unrelated GD patients was screened for seven previously described mutations: N370S (1226A→G), L444P (1448T→C), D409H (1342G→C), R463C (1504C→T), 1263del55, RecNciI, and RecTL. This allowed the identification of 77.4% of the GD alleles: N370S and RecNciI were the most prevalent mutations found (46.8% and 21% respectively). Southern analysis demonstrated three distinct patterns for the RecNciI alleles. In order to identify the remaining alleles, the full coding region of the gene, all the splice sites, and part of the promoter region were analyzed by singlestrand conformational polymorphism analysis (SSCP) after polymerase chain reaction amplification. This extensive screening allowed the identification of 13 different mutations, accounting for 93% of the total number of GD alleles. Three novel missense m u t a t i o n s , I 1 6 1 S ( 5 9 9 T → G ) , G 2 6 5 D (911G→A), and F411I (1348T→A), were detected. Twelve polymorphic sites within the glucocerebrosidase gene are in complete linkage disequilibrium and define two major haplotypes, ''-'' and ''+''. Mutation N370S was always associated with the ''-'' haplotype, as described in other populations. Interestingly, the RecNciI alleles with the same Southern-blot pattern were always as-sociated with the same haplotype. Am.