Fuzzy logic which was first introduced by Lotfi A. Zadeh in 1965, transcends the “black and white” approach of the Aristotelian logic, and tries to capture the wide grey areas of imprecision in between. This logic provides a mathematical approach to interpret the grey zones of imprecision. Some authors consider EBM and Fuzzy logic as two sides of a same coin. We believe that fuzzy logic approach is not in contrast to the EBM approach, but it is a complementary tool for a more realistic approach to the practice of evidence-based medicine. By merging and concurrent use of these two approaches (EBM and Fuzzy logic) in the process of decision-making, fuzzy logic can yield its suitable place in the field of medicine, considering the rapidly progression of EBM in this field. In this book we are trying to report our experience in integrating fuzzy logic in the decision process of VTE prophylaxis in hospitalized patients according to an Evidence-based risk assessment model (RAM), developed by Joseph A. Caprini. We believe that the application of Fuzzy thinking model in developing decision support systems can resolve most of the shortcomings of RAMs & practice guidelines.