No consensus exists as to who should be tested for thrombophilia, mainly due to the lack of good quality clinical outcome data in relationship to presence or absence of a given thrombophilia. Testing may be considered if (a) finding a thrombophilia predicts recurrent thrombosis and, thus, influences length of anticoagulation treatment decisions; (b) identifying a thrombophilia has implications on management of asymptomatic family members who are carriers of the detected thrombophilia; (c) a patient wishes to better understand why a thrombotic event occurred. Testing may be helpful in patients with venous thromboembolism at intermediate risk of recurrence in whom the finding of a strong thrombophilia can be one of the arguments for long-term anticoagulation--the "risk-of-recurrence-triangle" may be a useful aid in this decision process. Patients whose venous thromboembolism was provoked by a major transient risk factor should not be tested for thrombophilia. Thrombophilia tests should only be ordered by health care professionals who can provide the "4P": (a) appropriately select which patient to test, (b) provide pre-test counseling, (c) properly interpret the test results, and (d) provide education and advice to the patient. If testing is embarked on in patients with venous thromboembolism, it is advisable to be done at the time of decision making whether to stop or continue anticoagulation, i.e. typically after 3 months of anticoagulant therapy. Thrombophilia testing is best not done at the time of an acute thrombotic event and while a patient is on an anticoagulant.