ObjectivesTo make clear the roles of social interaction and social support in HIV infection among elderly men who visit female sex workers (FSW).MethodsWe conducted a case-control study: 106 newly HIV (+) vs. 87 HIV (-) elderly men who visited FSW with similar age, education levels, marital statuses, monthly expenses for entertainment and migration experiences. Experiences of visiting FSW, social interaction, and intimate social support were obtained. Backward binary logistic regression was applied.ResultsCases’ first visit to FSW happened at the age of 44.01 ± 12.25, older than controls (33.90 ± 13.43). 23.58% cases had gotten HIV-related health education (HRHE) before, less than controls (57.47%). More cases (48.91%) “always” got material support than controls (34.25%). Less cases gave “close” (38.04%) comments toward daily life, “satisfied” (34.78%) with their sexual life, “agree” being emotional fulfilled (46.74%) than controls (71.23% ,64.38%, and 61.64%). Risky factors for HIV infection among elderly men were having 3000 YUAN and above monthly income, visiting teahouse with friends, living without spouses, visiting different FSW, visiting FSW for other reason, receiving material support from most intimate sexual partner, older age of first visit to FSW. The protective factors were receiving HRHE, visiting FSW due to loneliness, and giving positive comments toward daily life with most intimate sexual partner.ConclusionsElderly men’s social interactions are mainly visiting teahouse which is a potential sexual venue. Getting HRHE is formal protective social interactions but very rare for cases (23.58%). Social support from sexual partner is not enough. Emotional support is protective meanwhile material support only is risky for becoming HIV-positive.