Staff development programs aiming to effect meaningful change are often short-lived and fail to promote teacher growth due to (1) lack of teacher control over program content; (2) the difficulty of influencing long-term changes in teachers' classroom behavior; and (3) the problem of documenting behavior change. This paper discusses a client-centered staff development program stressing ongoing professional growth and learning currently used in reading program improvement in several Florida schools. After exploring the research-based origins of the client-centered approach, the paper presents a model providing for (1) an extensive diagnosis of present instructional problems; (2) a careful selection from among alternative methods and materials; (3) extensive teacher involvement; (4) open, direct, two-way communication; and (5) a flexible implementation schedule. The client-centered approach is oriented toward inquiry and change as an emergent process. The model is adaptive because all three stages (diagnosis, testing, and implementation) emphasizes environmental feedback and flexible planning. A particular goal is shaped as a result of feedback from all involved. A case study employing all three stages is presented to illustrate the process. The client-based approach to staff development prioritizes the process of improving teachers' decision-making skills and enhancing their professional autonomy and collegiality. Included are one figure and seven references. (MLH)