This report is the first part of a two-part study designed to measure the training impact of employment under National Institutes of Health (NIH) research grants on graduate students and postdoctorals in training status. Using the NIH Research Grant Manpower Survey as a data base, hypotheses were investigated dealing with the relationship of individual characteristics and the type of research grant to the amount of support received from the grant and time spent working on the NIH research project. Some conclusions were: (1) Time spent (both total and paid hours) on a research project funded by an NIH grant is affected by educational background and personal characteristics, (2) The amount of financial support received from the project is related to educational background and personal characteristics, particularly for academic doctoral candidates, (3) Educational background and personal characteristics have little or no effect on the amount of unpaid work performed by postdoctorates but is often significant for academic predoctorates, and (4) There is a strong relationship between the individual's field of study and the primary scientific discipline of the research project, with academic postdoctorates more likely to work on grants within their field. Results supporting these conclusions are presented and discussed. (SB)