Falling of instruments is seen as a major problem and defect in the most surgical procedures that leads to an increase in operating time, surgical flow disruptions, more cost and possible damage to surgical instruments. The aim of this study was to analyze and compare statistically the incidence of accidental fall of instruments during neurosurgical, general, gynecological, orthopedic and urological operations. In this cross-sectional study, the prevalence of steel surgical instruments downfall during 100 open surgical operations was recorded. The data were recorded by intra operative observation using a self administered checklist which were confirmed. Data were then analyzed by SPSS software version 18 and descriptive tests. A total of 55 instruments falling were recorded. The results of this study showed that the most frequent number of instruments falls was in supine position and abdominal region. The causes of instruments' fall in control (49.1%) was related most commonly to time that the tools were left on the side of the patient body at a reachable region and ignoring instruments dropped on the floor (80%) was the most common condition after falling surgical instruments in both groups. Documentation of intra operative falling of instruments provides a basis for the development of solutions for improving operating room efficiency.