Introduction: Control of infections in the operation theatre is of utmost importance. Postoperative infections can be caused by a contaminated environment, unsterile equipment, contaminated surfaces, and infected personnel as well as contaminated disinfectants. Microbiological surveillance is an effective tool for identifying and controlling infections. Objectives: The purpose of this study is to identify bacterial colonization of surfaces and equipment and to determine the microbial contamination of air in the OTs of a tertiary care hospital. Materials & Methods: One year of retrospective analysis of the data obtained from routine microbiological surveillance of the all OTs of the hospital was done. OTs were deep cleaned as per standard CDC guideline (1) and post deep cleaning surveillance swab culture samples were collected. Aerobic bacterial culture of the samples was processed following standard guideline(1,2). Surveillance swab were collected from the different sites of OTs and immediately transported to the microbiology laboratory. An aerobic swab culture plates were incubated in incubator at 37ºC temperature for 48 hours and examined daily for bacterial growth.