The risk of venous thrombosis and need for prophylaxis in patients having undergone minimally invasive procedures and in patients immobilized in a leg plaster are poorly defined. We performed a literature search to evaluate the risk of developing venous thromboembolism after 2 minimally invasive procedures, laparoscopic surgery and arthroscopy, and in patients with lower limb plaster casts. Despite problems of "contamination" because some surgeons use prophylaxis in some of these patients, we were able to determine that (1) laparoscopic cholecystectomy can be considered a low-risk procedure and therefore routine use of prophylaxis is probably not justified; (2) patients undergoing arthroscopic knee surgery are at low to moderate risk and thus prophylaxis is optional; and (3) patients with plaster cast immobilization because of trauma have a moderate risk of thrombosis and should receive prophylaxis.