Since the ultimate effectiveness of any health care encounter rests in the provider's ability to gain the compliance of his or her client toward the prescribed medical treatment, a study compared clients' perceptions of the compliance-gaining strategies of both physicians and nurse practitioners, and investigated whether these perceptions were mediated by clients' self-reported health locus of control, or by seriousness of illness. Subjects, 121 students at a large midwestern university who had visited the campus Student Health Center within the last 4 months, rated compliance-gaining strategies for both physicians and nurse practitioners across three health care scenarios. The three scenarios represented the extremes and the median in subjects' severity of illness ratings of 10 health care scenarios. Results indicated that subjects perceived physicians more favorably than nurse practitioners in their use of the "request for feedback" strategy across all three health care scenarios. Nurse practitioners were perceived more favorably than physicians in their use of the "reassurance and empathy" strategy in one of the three scenarios. Perceptions of physician and nurse practitioner use of the remaining four strategies did not differ significantly. In addition, self-reported locus of control did not discriminate subjects' perceptions of health care provider, compliance-gaining strategy, or severity of illness. (Nine tables of data are included; 47 references and three appendixes--containing a list of compliance-gaining strategies, a health locus of control scale, and the 10 medical scenarios--conclude the study.) (SR)