Preclinical and phase I/II studies gave the proof of principle of enzyme replacement therapy (ERT) with recombinant alpha-galactosidase A through the demonstration of the clearance of the accumulated subtrate from plasma and tissues. In a multicenter, randomized, placebo-controlled, double-blind phase Ill study, the biological efficacy of recombinant alpha-galactosidose A (agalsidase beta 1 mg/kg/714 days) was demonstrated on the basis of complete clearance of accumulated globotriaosylceramide from the endothelia of the kidney, heart and skin. The phase III extension study data gives additional results: kidney function appears to be stabilized after 54 to 60 months of treatment with agolsidase beta in most patients. Intent-to-treat analysis of a double-blind, randomized, placebo-controlled, phase IV study, showed that, adjusted for on imbalance in baseline proteinuria, agalsidase beta significantly reduces by 53% the risk of a first clinical event (renal, cardiac and cerebrovascular), compared with placebo. Clinical benefits of ERT depend on patients' clinical status at baseline, therefore prompting for onset of ERT before irreversible damage occur and underlying the need to stratify patients' populations to better understand the outcome of ERT.