This protocol was developed in order to obtain bone marrow stem cells for ex vivo transduction with retroviruses containing the human glucocerebrosidase gene. We continue to enter a small number of patients to this protocol each year. Studies with the bone marrow hematopoietic progenitor cells have enabled us to identify the most effective retroviral construct currently available in order to carry out gene therapy trials in patients with Gaucher's disease. The data revealed that a comparatively simple retroviral construct containing human glucocerebrosidase cDNA driven by the MoLV promoter is highly effective. We have obtained approval and initiated a Phase I safety and gene marking investigation in patients with Type I Gaucher's Disease.