The invention features a method of producing a high mannose glucocerebrosidase (hmGCB) which includes: providing a cell which is capable of expressing glucocerebrosidase (GCB), and allowing production of GCB having a precursor oligosaccharide under conditions which prevent the removal of at least one mannose residue distal to the pentasaccharide core of the precursor oligosaccharide of GCB, to thereby produce an hmGCB preparation. Preferably, the condition which prevents the removal of at least one mannose residue distal to the pentasaccharide core is inhibition of a class 1 processing mannosidase and/or a class 2 processing mannosidase. The invention also features an hmGCB preparation and methods of using an hmGCB preparation.