Business integration is becoming one of the necessities in the ever-changing computing landscape. Web services and composition of web services have been introduced to address this necessity. A composite web service built using multiple component web services defines a business process. The process definition is expressed using one of the Web Service specification languages, such as BPEL4WS, BPML, and WSCI. Even though the composite web service invokes other services that are distributed across the Web, the orchestration systems created so far have been centralized. However, considering the number of business processes in an enterprise and the growth of the business volume in terms of the number of the business process instances, the performance, throughput, and scalability have been some of the major challenges for orchestration system designers. This thesis addresses the above concerns by providing the orchestration of a composite web service in a distributed environment. DO4WS is an implementation of a distributed orchestration engine for web services, which is flexible and scalable.