The wide spectrum of clinical manifestations resulting from glucocerebrosidase deficiency complicates genetic counseling for Gaucher disease. The identification of mutations in the glucocerebrosidase gene has enabled studies of genotype-phenotype correlation. However, a genotypic analysis of 60 type 1 and type 3 Gaucher patients reveals that the 5 most common Gaucher mutations, N370S, L444P, R463C, 84insG, and IVS2 + 1 G-->A, can be found both in patients with and without neurologic manifestations. Moreover, although some generalizations can be made about mutations that are more frequently encountered in particular patient populations, Gaucher patients sharing identical genotypes can exhibit considerable clinical heterogeneity. Thus in considering rationale for population screening one cannot rely solely on PCR determined DNA mutation analysis to reliably predict prognosis in Gaucher disease.