N‐Butyldeoxynojirimycin (NB‐DNJ, miglustat ‘Zavesca’) is an orallyactive iminosugar which inhibits the biosynthesis of macromolecular substrates that accumulate pathologically in glycosphingolipidoses. Clinical trials of NB‐DNJ in patients with Gaucher's disease demonstrate the therapeutic potential of such substrate inhibitors in the glycolipid storage disorders. However, macrophage‐targetted enzyme replacement using intravenous mannose‐terminated human glucocerebrosidase (imiglucerase, Cerezyme) is highly effective in ameliorating many of the manifestations of Gaucher's disease and is a treatment in widespread use. Given that imiglucerase and miglustat are now both licensed for the treatment of Gaucher's disease, there is a need to review their therapeutic status. Here the treatment of type 1 (non‐neuronopathic) Gaucher disease is evaluated with particular reference to the emerging role of oral N‐butyldeoxynojirimycin (miglustat) as a substrate‐reducing agent. This position statement represents the consensus viewpoint of an independent international advisory council to the European Working Group on Gaucher Disease.