The authors summarize the current knowledge in the area of novel risk factors for venous thrombosis, both genetic and acquired causes of hypercoagulability. Because the list of genetic defects that predispose carriers to develop thrombosis has increased significantly in recent years, along with the available assays to test for them, hypercoagulability has been a subject of much discussion. This review highlights the issues on hypercoagulability that pathologists who are not specialists in coagulation should be familiar with, in order to provide consultation to other physicians. An educated approach to the diagnosis of this newly described group of disorders will ensure more cost-effective and efficient care to patients at risk. © 2001 W.B. Saunders Company.