Preparing healthcare professionals for teaching is regarded as essential to enhancing teaching effectiveness. Although many reports describe various faculty development interventions, there is a paucity of research demonstrating their effectiveness. To synthesize the existing evidence that addresses the question: "What are the effects of faculty development interventions on the knowledge, attitudes and skills of teachers in medical education, and on the institutions in which they work?" The search, covering the period 1980-2002, included three databases (Medline, ERIC and EMBASE) and used the keywords: staff development; in-service training; medical faculty; faculty training/development; continuing medical education. Manual searches were also conducted. Articles with a focus on faculty development to improve teaching effectiveness, targeting basic and clinical scientists, were reviewed. All study designs that included outcome data beyond participant satisfaction were accepted. From an initial 2777 abstracts, 53 papers met the review criteria. Data were extracted by six coders, using the standardized BEME coding sheet, adapted for our use. Two reviewers coded each study and coding differences were resolved through discussion. Data were synthesized using Kirkpatrick's four levels of educational outcomes. Findings were grouped by type of intervention and described according to levels of outcome. In addition, 8 high-quality studies were analysed in a 'focused picture'. The majority of the interventions targeted practicing clinicians. All of the reports focused on teaching improvement and the interventions included workshops, seminar series, short courses, longitudinal programs and 'other interventions'. The study designs included 6 randomized controlled trials and 47 quasi-experimental studies, of which 31 used a pre-test-post-test design. Despite methodological limitations, the faculty development literature tends to support the following outcomes: Overall satisfaction with faculty development programs was high. Participants consistently found programs acceptable, useful and relevant to their objectives. Participants reported positive changes in attitudes toward faculty development and teaching. Participants reported increased knowledge of educational principles and gains in teaching skills. Where formal tests of knowledge were used, significant gains were shown. Changes in teaching behavior were consistently reported by participants and were also detected by students. Changes in organizational practice and student learning were not frequently investigated. However, reported changes included greater educational involvement and establishment of collegiate networks. Key features of effective faculty development contributing to effectiveness included the use of experiential learning, provision of feedback, effective peer and colleague relationships, well-designed interventions following principles of teaching and learning, and the use of a diversity of educational methods within single interventions. Methodological issues: More rigorous designs and a greater use of qualitative and mixed methods are needed to capture the complexity of the interventions. Newer methods of performance-based assessment, utilizing diverse data sources, should be explored, and reliable and valid outcome measures should be developed. The maintenance of change over time should also be considered, as should process-oriented studies comparing different faculty development strategies. Faculty development activities appear highly valued by participants, who also report changes in learning and behavior. Notwithstanding the methodological limitations in the literature, certain program characteristics appear to be consistently associated with effectiveness. Further research to explore these associations and document outcomes, at the individual and organizational level, is required.