The lipid storage disorders have long been considered primary candidates for enzyme replacement therapy. This goal has been achieved with a remarkable degree of success in Gaucher's disease. Among the accomplishments that were important to obtain clinical benefit were the development of a large-scale procedure to purify human placental glucocerebrosidase and a method to target this enzyme to lipid-storing macrophages through glycoform modification. In addition, the effectiveness of recombinantly produced macrophage-targeted glucocerebrosidase has recently been demonstrated. Because macrophages originate from stem cells in the bone marrow, ex vivo transduction of these cells with retroviral vectors containing the cDNA for human glucocerebrosidase is being explored for the genetic therapy of Gaucher's disease.