Hypertrophic cardiomyopathy (HCM) is a cardiac disorder affecting 1 in 500 persons. The cardinal feature is (inappropriate) left ventricular hypertrophy in the absence of another identifiable cause. Sudden cardiac death (SCD) is the most devastating and feared complication and may be the presenting manifestation. The striking heterogeneity and unpredictability of HCM make risk stratification problematic and imprecise. Cases must be deferred to the FAA for third- or limited second-class special issuance consideration. In general, first-class and full second-class medical certification is not permitted.