The paper addresses a model, a framework, and an implemented system for supporting design activities where the use of case-based reasoning may reveal particular appropriateness. In the proposed environment, special attention is given to the synthesis of solutions by means of adaptation. A pragmatic combination of a number of artificial intelligence (AI) techniques, considering case-based reasoning (CBR) as the framing concept, enables the implementation of a system that conveniently supports most designers' cognitive needs. The design of highway bridges was the chosen domain of discourse, for it represents an excellent example for demonstrating the potential of analogy in design. Thus, a large base of real cases is built. The induction of new knowledge is performed by extraction, association, and regression processes. Finally, a real context is used to illustrate the use of the model and to demonstrate its utility and capabilities in supporting designers' decisions, particularly on the synthesis-i.e., adaptation-of solutions.