Venous thromboembolic disease (VTE), which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), is a common and preventable source of post-operative morbidity and mortality. The high incidence of VTE reflects both underutilization of standard thromboprophylactic regimens and also an incomplete understanding of how surgery and critical illness affect the risk of post-operative VTE over time. To date, prior investigations into time-to-VTE follow surgery are insufficient - they utilize arbitrary cutoffs for early versus delayed VTE and fail to specify how risk profiles and clinically relevant markers change over time in these patients. As such, our primary objective in this study is to identify clinically relevant variables associated with temporal trends in VTE by performing a multi-center retrospective analysis of post-operative PE distribution over time. In order to investigate this objective, we propose a retrospective study aimed at identifying all currently existing data from patients who developed post-operative VTE following index (surgical) admission. After completing this query, we plan to first analyze post-surgical VTE distribution over time utilizing a kernel density plot to determine viable cutoffs for early versus delayed events. Cox proportional hazards models will then be used within these categories to determine whether differences in co-morbidities, laboratory data, or blood product transfusion are associated with VTE. A competing risks analysis will be used to differentiate whether variables of interest remain associated with VTE after adjusting for in-hospital mortality. Heterogeneity of effects can be further explored by performing subgroup analyses based on patient age, gender, race, and type of operation. Further, we also plan to use this analysis to stratify PE occurrence by time of diagnosis in order to evaluate how severity of PE, risk of 30-day mortality, and treatment vary based on time of diagnosis. Finally, we plan to compare how choice, timing, and dose of prophylaxis differs between early and delayed VTE cohorts. Completion of this research protocol will likely shed light in temporal trends in VTE that may yield critical information for the development of a more individualized approach to prophylaxis for VTE.