Numerous expert systems (ES) applications have been developed in the field, yet at this time no systematic, computerized tool for ES development planning exists. In this article, we present an ES development planner that adopts the constraint and rule satisfaction problems framework. We represent knowledge concerning ES development planning with objects, constraints, and rules under multiple objectives. We also present a unified reasoning process to obtain a consistent ES development plan, which has the following features: (1) supporting user interaction to reflect user intention about the problem situation and to resolve conflicts between objectives; (2) concurrent reasoning with multiple starting points to enhance the search efficiency; and (3) integrated reasoning encompassing the backward chaining popularly used in the rule-based systems and constraint propagation methods developed for constraint satisfaction problems. A prototype system ES* is developed using the tool UNIK and LISP language on a SUN 4 SPARC workstation, and an application on tax advisory expert system development planning is illustrated.