Objectives: Inclusion of infectious disease (ID) physicians in the care of patients with possible infection can favorably affect antibiotic usage. The aim of this study was to evaluate the role of the ID consultations in reducing inappropriate antibiotic usage. Materials and Methods: This is a prospective study evaluating all adult ID consultations from January 2006 to December 2009. A total of 1444 consultation requests were recorded during the 4-year period. Results: The most frequent consultations were from cardiology (23.1%), orthopedics (8.2%), general medicine (7.8%), hematology-oncology (7.8%), gastroenterology (7.3%), and pulmonary/critical care (7.1%). The main reason for consultation was for the choice of antibiotics (75%). The commonest diagnoses prior to consultation were fever (14.7%), bacteremia (9.1%), and urinary tract infection (8.4%). Bacteremia was documented in 21.4% of cases and 12.9% were found to have no identifiable focus of infection. Antimicrobial therapy was changed in 58.7% and antimicrobials were discontinued in 14.7% of cases. The number of antimicrobial therapy was one (49.7% and 49.9%) and two (24% and 17.6%, P = 0.0001) before and after the consultation, respectively. In addition, 17.3% and 26.9% ( P = 0.0001) received no antimicrobial agents before and after ID consultation. Conclusion: ID consultation is important to reduce inappropriate antimicrobial therapy and to limit the number of dual therapy.