This paper describes the effect of a person's social network upon his or her use of health services. A "social network" consists of complex strands of affiliations radiating from an individual to his/her close associates (kin and friends) and then to the larger society beyond. Health services include hospitals, clinics, doctors' offices, and telephone contacts to those places. Approximately 1200 adults in the Los Angeles area were interviewed during 1976 concerning people they most often talked to about personal health problems. For each person mentioned by the respondents, information was obtained on their relationship to the respondent, age, proximity of residence, frequency of visits, degree of support usually given in problem situations, and whether the respondent would consult them about health matters. Extensive data analysis determined respondents' network characteristics, use of networks in times of chronic or acute illness, and respondents' background characteristics. Results showed that females reported more network advice in favor of using health services and had larger networks than men, and younger respondents and higher socioeconomic groups had larger networks. Older respondents and females were most likely to use health services for chronic problems. Respondents with greater network contact in general were less likely to use health services for chronic problems. However, those reporting specific network advice to see a doctor were more likely to use health services for chronic problems. A conclusion is that the type of advice given by the social network, not the network structure, is important in predicting a person's use of health services. (Author/AV)