The first patient reported was a 33 years old male with clinical manifestations of Fabry's disease. The diagnosis was confirmed by ophthalmologic, histological and enzymatic studies. Because of inefficacity of treatment with plasma transfusions and of symptomatic therapies, a transplant of cells with normal enzymatic activities was envisioned. In this patient without renal failure, a renal transplant was not justified and a transplant of fetal liver cells was decided. The improvement of extra-renal manifestations of the disease with this new treatment was comparable to that obtained with kidney transplantation. In particular, objective and subjective clinical symptoms were significantly improved: sweating appeared became normal, cutaneous lesions appeared slightly decreased and pains disappeared. This improvement was still persistent 3 years after the fetal liver transplant, the viability of which was initially followed using dosages of circulating alphafoetoprotein. The second case-report is comparable. Fabry's disease was diagnosed in a 26 years old male on the clinical manifestations, the histological lesions and the enzyme deficiency. After failure of one plasma transfusion, the patient received a fetal liver transplant. It is still too early to evaluate the efficacy of the transplant in this second case, especially as the patient had normal sweating and relatively few pains except at the cold season. The mechanism which may be held responsible for possible improvement in our patients, as in recipients of a kidney transplant, is not completely elucidated. The cells, rather than steroids or azathioprine, seemed to support the efficacy. Was the enzyme activity exerted in situ? Was there a "colonization" by lysosomial enzymes? From the results observed after several years will derive the significance of this therapeutic approach in Fabry's disease, more generally, in many diseases associated with a genetic enzyme deficiency.