OBJECTIVES: We examined relationships between social capital and health service measures among low-income individuals and assessed the psychometric properties of a theory-based measure of social capital. METHODS: We conducted a statewide telephone survey of 1216 low-income New Mexico residents. Respondents reported on barriers to health care access, use of health care services, satisfaction with care, and quality of provider communication and answered questions focusing on social capital. RESULTS: The social capital measure demonstrated strong psychometric properties. Regression analyses showed that some but not all components of social capital were related to measures of health services; for example, social support was inversely related to barriers to care (odds ratio=0.73; 95% confidence interval=0.59, 0.92). CONCLUSIONS: Social capital is a complex concept, with some elements appearing to be related to individuals' experiences with health services. More research is needed to refine social capital theory and to clarify the contributions of social capital versus structural factors (e.g., insurance coverage and income) to health care experiences.