Thromboembolism is a rare complication of ovarian stimulation for IVF. However since venous thrombosis is a potentially serious disorder, all patients proceeding to IVF treatment should be individually assessed for their risk of thrombotic complications. As the presence of thrombophilia constitutes an important risk factor, plasma AT, proteins S and C, anti-phospholipid antibodies, Factor V Leiden mutation and MTHFR 677T should be measured in patients with additional risk present. These risks include a previous thrombotic event or a family history of thrombosis, the development of OHSS and age over 40 years. Thromboprophylaxis should be considered in women with a previous DVT, women who develop OHSS and in women over 40 years with a thrombophilia. In addition, women who develop serious infections or immobilization due to surgery should receive thromboprophylaxis. Compression stockings and low-molecular weight heparin constitute first line thromboprophylaxis. Thromboprophylaxis should normally commence 48 hours after oocyte pick-up to reduce the risk of haemorrhagic complications. This should be extended throughout the first trimester. In cases where thrombophilia has been detected, consideration should be given to extending prophylaxis throughout pregnancy.