Eleven randomly selected freshmen medical students early in their first semester interviewed trained simulators portraying "mothers" and their interviewing skills were objectively recorded by making use of an interaction analysis and an appraisal of amount of organic and interpersonal data collected. These students were longitudinally observed during the subsequent three years. Significant differences in interviewing skills were noted in mean performances in comparison to randomly selected seniors, pediatric residents, and a control group of peers. Freshmen and juniors exceeded sophomores, seniors, and residents in ability to gather interpersonal data. Proficiency in collecting organic related data was demonstrated by juniors, seniors, and residents. Overall, the most productive and efficient interviewers were the juniors. Profiles have been constructed which assist in developing needed educational experiences with appropriate emphasis and timing to permit the development and retention of vital interviewing skills.