Case-based planning (CBP) is a problem-solving method that uses a library of cases, where a case associates a past problem and goal description with a plan that solves the problem by achieving the goal. Given a new problem, CBP systems retrieve one or more cases that solve similar problems and adapt the retrieved cases' plans to achieve the new goal. Case retrieval involves intelligent search of the case library. Plan adaptation can include steps copied from the retrieved case plans and steps derived by other means, such as first-principles planning. Important relationships exist between the technology that measures similarity during case retrieval and the technology that performs effective adaptation during case reuse. However, we concentrate here on the adaptation process itself.