We present a case study in framework based software development, with specific analysis of the effect of learning on productivity and defect density. The framework supports the development of multimedia, web-based services on a digital network. It uses a CORBA infrastructure, is developed in Java, and integrates COTS (Component Off-The-Shelf).The case study considers the development of the framework and the development of a number of applications reusing the framework. Some of the applications are also developed without the framework. The study uses a nested factors experimental design, and measures effort, application size, defects, productivity, reuse level.The main result of the study is the correlation found between framework learning and productivity increase; and between framework learning and defect density decrease. We also underline an impressive difference in productivity between traditional development, development of the framework and development with the framework.