Experience in reengineering a legacy application into a web based J2EE system with modified Rational Unified Process (RUP)is presented.RUP is adopted into an onsite-offshore development model along with ISO 9001 and SEI CMM Level 5 standards.The new application has above 2500 code components and the effort is about 100 person years.For the benefit of software development community,some of our experiences in design,development,testing and project management are elaborated as generalized concepts.We have demonstrated that development process could be improved with lessons learnt from the initial iterations. The three views of a web application are explained and the translations between the layers are discussed.Benefit of continuous integration is highlighted.Various types of dependencies to be taken into account for sequencing the development are elaborated.The levels of testing in iterative development are mentioned.The importance of adaptive team structure and various parameters guiding iteration planning are dealt with.A simple estimation model based on types of transactions is presented. Finally,a fine grained risk management concept that can integrate with the development process is proposed.