Venous thromboembolism (VTE) is common in patients with advanced cancer and may influence patient eligibility for clinical studies, quality of life, and survival. We reviewed the medical records of 220 consecutive patients seen in the Phase I Clinical Trials Program at M. D. Anderson Cancer Center to determine the frequency of VTE, associated characteristics, and clinical outcomes. Twenty-three (10.5%) patients presenting to the Phase I Clinic had a history of VTE; 26 (11.8%) patients subsequently developed VTE, with a median follow-up of 8.4 months. These included nine (39%) patients with and 17 (8.6%) without a history of VTE (P < 0.0001). The most common events were deep venous thromboses of the extremities and pulmonary emboli. The median survival of patients with and without a history of VTE was 4.7 and 10.9 months, respectively (P = 0.0002). Multivariate analysis demonstrated that a history of VTE (P < 0.0001), pancreatic cancer (P = 0.007), and platelet count >440 x 10(9)/L (P = 0.026) predicted new VTE episodes. In conclusion, this retrospective analysis demonstrated that a history or new development of VTE was noted in 40 (18%) of 220 patients seen in our Phase I Clinic. A prognostic score that can be used to predict time to development of and frequency of VTE is proposed. Am. J. Hematol. 2009. (c) 2009 Wiley-Liss, Inc.