Hospital-acquired deep vein thrombosis (DVT) and pulmonary embolisms (PE) are preventable problems that can increase mortality. Early assessment and recognition of risk as well as initiating appropriate prevention measures can prevent DVT or PE. The purpose of this research project was to develop a DVT risk assessment tool and test the tool for validity and reliability. Three phases were undertaken in developing and testing the JFK Medical Center DVT risk assessment tool. Investigation and clarification of risk and predisposing factors for DVT were identified from the literature, expert nursing knowledge, and medical staff input. Second, item development and weighting were undertaken. Third, parametric testing for content validity measured the differences in mean assessment tool scores between a group of patients who developed DVT in the hospital and a demographically similar group who did not develop DVT. Interrater reliability was measured by having three different nurses score each patient and compare the differences in scores among the three. The DVT group had significantly higher scores on the JFK DVT assessment scale than did those who did not experience DVT. Interrater reliability showed a strong correlation among the scores of the three nurses (.98). Providing a valid and reliable tool for measuring the risk for DVT or PE in hospitalized patients will enable nurses to intervene early in patients at risk. Basing DVT risk assessment on the evidence provided in this study will assist nurses in becoming more confident in recognizing the necessity for interventions in hospitalized patients and decreasing risk. Nurses can now evaluate patients at risk for DVT or PE using the JFK Medial Center's risk assessment tool.