Many small and medium enterprises started developing web business systems based on Service Oriented Architecture. Since SOA propaganda has created enormous impact across industries many enterprises started evaluating SOA approach. Especially enterprise service bus (ESB) architecture tools have excellent appreciation since it helps to build services without much effort. But it has also created a wrong impression in the field that any service requirement can be build using ESB. I personally feel that ESB is not for all service development. So I wish to explore here about role of ESB in various enterprise needs. Before go into the SOA-ESB approach, let us see what can we expect out of ESB. Enterprise service bus provides protocol binding components, application adapters, in-built transformation engine, routing engine, messaging and service engine. All helps to achieve integration, messaging and data transformation solutions across applications, networks based on SOA approach. ESB has been innovated to play as communication backbone across enterprise infrastructure. So ESB can provide excellent support in building communication channels across enterprise systems. EAI and SOI: As per wikipedia “Enterprise Application Integration (EAI) is defined as the use of software and computer systems architectural principles to integrate a set of enterprise computer applications.” Many realized that prior approaches like point to point integration, native language integration; remote method call does not add value like service based approach. Now days, many integrations are done based on service oriented architecture. So service based integration with the help of ESB and other components also called as service oriented integration (SOI). Enterprise service bus plays a major role in service based integration since the fundamental need of protocol binding, message transformation and mediation can be achieved easily through ESB. Many ESB vendors provide adapters for integrating various packaged and legacy applications. So the predominant role of ESB is to act as integration and communication medium across enterprise business and legacy systems. ESB in Service Oriented Business Application: As mentioned earlier, many IT departments wishes to realize the benefit of SOA. Many initiated to build enterprise web applications based on SOA. The role of ESB for such web application architecture differs from integration architecture. ESB can play as mediator role between the web applications and other infrastructure elements like Email, FTP, packed applications and partner services. But ESB should not be used to build a data access or business service layer for the web application. MVC based web architecture is a proven methodologies for web application development. Building the model layer by ESB is not a recommended approach. Of course ESB can easily build data access services for a database system. But it does not effectively supports persistence, session and transaction management between web and database layers. ESB can be used for scenario like building a data wrapper services for legacy and packaged applications. So, for service oriented business application requires ESB only if it requires to wrap the existing legacy and packaged applications. Building web application with service components is a good approach until unless you are building with business processes. BPM can play a major role in web architecture if the application scope includes business processes. Using ESB and BPM for simple web application does not add any value or benefit to the enterprise. SOA and BPM will provide enormous support and benefits if deployed at enterprise level. For further clarification and suggestions please reach me. I am happy to help our community.