The study identifies operational risks within service-oriented architecture (SOA) of information systems. As a part of operational risks a new error classification scheme is proposed for SOA applications. It is based on errors of the information systems which are service providers for application with service-oriented architecture. The proposed classification approach was used toclassify system errors from two different enterprises (oil and gas industry, metal and mining industry).Besides we conducted a research to identify possible losses from operational risks and estimated losses for each error group per day.