A viable treatment for lysosomal storage disease has been very difficult to attain. One option is pharmacological inhibition of synthetic pathways to reduce substrate accumulations. Miglustat N-butyldeoxynojirimycin (NBDNJ), an inhibitor of glucosylceramide synthase, has shown much promise in clinical trials for the treatment of Type I Gaucher disease. The molecular events invoked by NBDNJ in cell culture and in animal models have not been so definitive. This review discusses the biochemical and molecular impact of NBDNJ as it relates to its potential as a therapeutic drug.