AIMS: Anderson-Fabry disease affects various organ systems due to glycosphingolipid accumulation. Enzyme replacement therapy (ERT) has been reported to decrease left ventricular wall thickening (LVWT) and to improve diastolic dysfunction. METHODS AND RESULTS: This prospective study included 29 patients (patients; mean age 37 +/- 13 years) with genetically, enzymatically and/or biopsy-proven Anderson-Fabry disease and long-time ERT. Data on symptoms, cardiac medications and history of hypertension were collected and all patients had comprehensive echocardiographic examination prior to ERT and at follow-up. Disease was at an early stage with a total mean Mainz severity score index of only 18.6 +/- 13.0. Prior to ERT, 79% of patients reported acroparesthesia. The median creatinine level was 121 +/- 108 mcmol/L and LVWT was present in nine patients (31%). Binary appearance of the interventricular septum was found in 20% and posterobasal fibrosis in 83%. At median follow-up of 37 months, acroparesthesia decreased to 55% (P = 0.016). There was no change in creatinine levels. The incidence of LVWT was unchanged, only an increase in interventricular septal wall thickness from 11.7 +/- 0.4 to 12.5 +/- 0.5 was observed (P = 0.009). Left atrial size and the percentage of patients with binary appearance and posterobasal fibrosis were unchanged. There was a small improvement in diastolic function (29% decrease of E/Ea; P < 0.002). CONCLUSION: Our Anderson-Fabry cohort had successful long-time ERT with impressive amelioration of subjective symptoms. Although there was not much improvement in cardiac changes apart from a slight improvement of diastolic function, at least, there was no progression of cardiac disease. For complete reversibility of cardiac changes in Anderson-Fabry disease, ERT might have to be started earlier in life and/or prescribed for a longer time.