The structural gene for human acid beta-glucosidase (GBA) has been regionally assigned to a narrow region on chromosome 1 using somatic cell hybridization, specific immunoprecipitation, and assay with the natural substrate. A human fibroblast line, 46,XX,del(1)(pter leads to q42:), was fused with mouse RAG fibroblasts and the heterokaryons were subcloned. All hybrid subclones containing a normal chromosome 1 were positive for GBA. In contrast, subclones with a single del(1) were negative for GBA by both immunoprecipitation and natural substrate assays. These results were consistent with the previous assignment of GBA to the region 1p11 leads to qter and further localized the gene to the narrow region 1q42 leads to qter.