Coronary artery disease (CAD) has a strong genetic component, but is also greatly influenced by environmental factors such as diet and smoking, and disorders such as diabetes mellitus and hypertension. This interaction makes prediction of CAD risk generally difficult. However, in familial hypercholesterolaemia (FH), risk of early CAD is considerably increased by the mutation of a single gene, and genetic testing may be appropriate. We summarize current knowledge concerning DNA-based tests in the identification and management of FH, and propose specific recommendations for genetic testing and further research. The major value of DNA tests for FH is in genetic tracing programs to identify and treat affected individuals. DNA testing is appropriate for: (a) diagnosis of FH when physical signs or family history are equivocal or absent (important given the increased risk of CAD associated with FH compared to other hypercholesterolaemias); (b) detection of a mutation causing FH in immediate family members (particularly children) where there is a family history of premature CAD. A positive DNA-based test for a mutation is especially useful in children, in whom plasma lipid levels may not be diagnostic. Current clinical practice is to test relatives for raised cholesterol. Testing for mutation carriers in distant relatives, although feasible, is not currently recommended. Research projects should now be started to address two issues: (i) whether genetic tests for FH better predict clinical outcome than does measurement of plasma lipid levels; (ii) whether genetic testing for FH confers overall benefit both to the patient and their relatives, and to the NHS. Answers to these questions will guide the subsequent development and implementation of genetic tests for CAD risk in general, if and when the considerably more complex genetic causes of CAD are identified.