Modern methods of examining plasmatic clotting parameters, and especially the fact that specific mutations can now be demonstrated, have resulted in the possibility of reaching an accurate diagnosis in about 60% of all patients with a thrombophilic diathesis. Women affected should be advised against using combination preparations for oral contraceptionas a matter of principle, since this could increase the risk of thrombosis by a factor of 3. Since in about 40% of patients with thrombophilia it is not possible to demonstrate any specific clotting disorder, risk assessment for potential users of oral contraception is still based mainly on clinical judgement, family and personal history and the presence of acquired risk factors.