A comparison of different ethnic groups in New York City reveals significant variations in knowledge about disease, attitudes toward medical care, and behavior during illness. These differences are found to be related to the form of social organization within the ethnic groups. The more ethnocentric and socially cohesive the group on a community, friendship, or family level, the more likely are its members to display low knowledge about disease, skepticism toward professional medical care, and dependency during illness. In general, form of social organization is found to be more important than ethnicity or social class in relation to sociomedical responses.