Fabry disease was initially believed to be a very rare disorder, but an increase in prevalence following screening studies revealed that it may be more frequent in a less severe (nonclassical) variant. The adult physician can encounter both phenotypes: classical disease arising in childhood, or after establishing the diagnosis in an adult male. The nonclassical phenotype is usually diagnosed after additional investigations in a patient with renal disease or left ventricular hypertrophy (LVH) of unknown origin. Enzyme replacement therapy (ERT) appears to have a modest effect in Fabry disease, and many challenges remain both in understanding the pathophysiology and natural history as well as in improving patient outcomes.