Background: Venous thromboembolism (VTE) is a leading cause of mortality in patients with cancer. Characterisation of VTE in cancer will guide prophylactic anti-coagulation of high risk populations. Methods: We performed a retrospective analysis using electronic patient records, of 910 upper GI (UGI) cancer and 1,299 colorectal cancer (CRC) patients referred to a tertiary cancer centre to identify the incidence of VTE, its relationship to chemotherapy and impact on survival. VTE risk scores were calculated using the Khorana index (Khorana AA et al. Blood 2008 May 15;111(10):4902-7). Results: VTE were identified in 88/910 (9.7%) patients with UGI cancer (oesophageal 37%, gastro-oesophageal 24%, gastric 39%), comprising 50 deep vein thromboses (DVT) and 43 pulmonary emboli (PE). 52% were stage I-III and 48% stage IV. 56% of patients received chemotherapy up to 4 weeks before VTE. Median time to VTE from cancer diagnosis was 5.3 months (range -3 to 31.2). No difference in survival was seen for patients with VTE compared to a stage matched control group without VTE (median OS 12.5 v 9.4 months, log rank p=0.2). VTE (DVT:PE, 69:49) affected 115/1299 (8.9%) patients with CRC (25% stage I-III, 75% stage IV). Median time to VTE from CRC diagnosis was 5.4 months (range -4.3 to 54.5) for stage I-III and 8.6 months (range -4.3 to 77) for stage IV CRC. Chemotherapy was received by 41% (stage I-III) and 78% (stage IV) of patients within 4 weeks before VTE. Data to perform VTE risk score were available for 72/115 CRC patients with VTE, which classified 61.1% as low-risk (stage I-III 81.2% (13/16); stage IV 55.3% (31/56)). Again, no difference in survival was seen for patients with VTE compared to a control group without VTE matched for stage and performance status (median OS for stage I-III, 40 vs. 50.3 months p=0.41; stage IV, 20.7 vs. 18.8 months, p=0.52). Conclusions: VTE affects nearly 1 in 10 patients with GI cancer receiving chemotherapy. The peak incidence is in the first 6 months following diagnosis. Most patients have DVT and 36% are asymptomatic. No adverse impact on survival was seen for patients with VTE compared to stage matched controls implying VTE is not a prognosticator of poor outcomes in gastrointestinal cancers. Mature data will be presented at the meeting.