In summary, Our findings indicate that the research project grant programs of NIH have consistently provided opportunities for newly trained scienitists to receive support for biomedical research projects that they have initiated themselves. The system encourages progress in the biomedical sciences through the continuous influx of creative individuals who can explore their own research ideas, ideas that also correspond to the health research needs of the nation as reflected by the categorical missions of the institutes. Despite the decline (approximately 20 percent) in the total number of active research projects over the past 7 years. the proportion of new PI's among all recipients of new awards remained fairly constant from year to year. From 1966 to 1972, an average of 57 percent of all new research project awards were received by PI's entering the system for the first time, while an average of approximately 10 percent of all the PI's on research projects each year were new PI's being supported by NIH for the first time.