At the request of the National Institutes of Health (NIH) the Committee on National Needs for Biomedical and Behavioral Research Personnel conducted a study of the career achievements of NIH postdoctoral trainees and fellows. Findings from this report will be used to formulate recommendations on training in the committee's next report on research personnel needs. In separate assessments for holders of Ph.D. and M.D. degrees, the career achievements of former NIH postdoctoral trainees (supported via institutional training grants) and former NIH postdoctoral fellows (supported by individual awards from NIH) were contrasted to those of comparison groups without NIH postdoctoral appointments. Three types of achievement (research funding, research employment, and research publications) were examined. The investigation found that persons with NIH postdoctoral appointments were more likely to pursue research careers than their colleagues without NIH training and that they were more successful on almost all measures of career achievement. While the differences were most pronounced for the recipients of fellowship appointments, the recipients of NIH traineeship appointments were also more successful than those individuals without NIH appointments on most career achievement measures.