Surgery for colorectal cancer conveys a high risk of venous thromboembolism (VTE). The effect of thromboprophylactic regimens of varying duration on the incidence of VTE was assessed in 417 patients undergoing surgery between 2005 and 2009 for colorectal cancer. Low-dose unfractionated heparin (LDUH) was used in 52.7% of patients, low-molecular-weight heparin (LMWH) in 35.3%, and 10.7% received LDUH followed by LMWH. Pharmacological prophylaxis was continued after hospitalisation in 31.6%. Major bleeding occurred in 4% of patients. The 30-day mortality rate was 1.9%. The incidence of symptomatic VTE from hospital admission for surgery to 12 months after was 2.4%. There were no in-hospital VTE events. The majority of events occurred in the three-month period after discharge, but there were VTE events up to 12 months, especially in patients with more advanced cancer and multiple comorbidities.