The Canadian Fabry Disease Initiative [CFDI] is a longitudinal study evaluating all Canadians diagnosed with Fabry disease [FD]. The study has 3 cohorts: Cohort 1A which includes 81 subjects who were on enzyme replacement therapy [ERT] prior to October 2006, Cohort 1B which has ongoing enrolment of subjects newly started on ERT who are randomized to agalsidase alfa or agalsidase beta, and Cohort 1C where subjects who do not meet nationally accepted Canadian criteria for ERT are followed to assess the natural history of disease complications. The study currently enrols 244 patients [95 males and 149 females] with a mean age of 41.9+/-14.5years. There is a high prevalence of the c.427G>C mutation. Cohort 1A contains 82 patients [59 males, 23 females] of whom 42% are known to have cardiac complications of FD and 38% renal complications. Cohort 1B at the time of writing contained 37 patients [15 males, 22 females] of whom the indications for ERT were cardiac in 55% and renal in 60%. Cohort 1C at the time of writing contained 125 patients [22 males, 103 females]. Enrolment is ongoing in both Cohorts 1B and 1C. When compared to subjects in the Fabry Outcome Survey and the Fabry Registry, subjects in the CFDI are less likely to be male reflecting less ascertainment bias. The CFDI is a robust national data set that will contribute to available data on the natural history of FD and on the comparative efficacy of the two commercially available ERT products.