In this paper, we present an empirical investigation to measure the effects of various factors on operating loss in one of major Iranian banks called Bank Mellat. The proposed study of this paper uses a standard questionnaire and distributes it among 57 people who are mainly in top management levels. The questions are categorized into five groups including events related to the processes and methods, events outside the organization, related events within the organization and business disruptions and system failure. The results of our survey confirm that the loss associated with events related to the processes and methods increases operating risk meaningfully, the loss associated with business disruptions and system failure increases operating risk meaningfully and the loss associated with related events within the organization increases operating risk meaningfully. However, our survey do not confirm that the loss associated with events outside the organization increase operating, risk meaningfully. Finally, the preliminary survey of our analysis shows that there is not enough evidence to believe that the effects of business disruption and internal affairs are significantly different from the other event.