Notwithstanding recommendations and interventions, the percentage of 50-74-year-old U.S. women who reported having had a mammography in the past two years remained below target coverage. Social interactions may influence mammography rates. To measure characteristics of social interactions in a Midwestern city as they relate to social support for mammography received by women older than 40 years of age. A cross-sectional study was conducted in Bloomington, Indiana, sending mail surveys to 3,000 telephone directory addresses selected by simple random sampling. An anonymous, selfadministered, closed-ended, questionnaire with eight checklist items (for demographics) and six multipart semantic differential scale items (for social support), derived from validated instruments, was used. Social support for mammography in women who had undergone regular screening was analyzed using chi-square test and logistic regression. Of 450 respondents with valid responses, 91% were white; 47% were older than 80; 92% had good health insurance coverage; and 82% had undergone regular mammography. Healthcare workers provided the highest support, followed by children, siblings, and relatives. Friends, neighbors, and co-workers were least supportive. In social interactions, emotional support was the most prominent, followed by informational, appraisal, and instrumental supports. Having higher income and being married were associated with receiving greater support. Although mammography provides limited benefits after age 74, women older than 80 years of age received the highest support. Identifying the structural and functional characteristics of social interactions is important for: 1) designing interventions that enhance social support, and 2) expanding breast cancer screening via personalized approaches using existing social interactions.