Literature on medical care utilization by Mexican-Americans suggests that patterns of utilization can be explained, in part, by acculturation, social class and social isolation. The relative importance of these variables is explored in a survey of a rural Mexican-American community in Southern Texas. Data on 152 families are analyzed using a logit analysis, with utilization as the outcome variable. The results suggest that acculturation has a direct effect, while social class and social isolation interact to have a weak effect independent of acculturation. These results confirm the importance of understanding all three variables in planning and implementing medical care programs in Mexican-American communities.