This review summarizes recent information about the major thrombophilic conditions, their clinical relevance, and practical aspects pertaining to testing for these thrombophilias, such as when to test and what assays are appropriate. Conditions covered include factor V Leiden, prothrombin 20210 mutation, proteins C and S, antithrombin, antiphospholipid antibodies, homocysteine, and methylene-tetrahydrofolate-reductase enzyme mutation. Additional comments focus on education of patients and educational resources for patients, such as the National Alliance for Thrombosis and Thrombophilia (www.nattinfo.org).