The study presented here is an investigation of the importance of social interactions to perceptions of the risk of AIDS, and explores spousal communication about the AIDS epidemic in rural Malawi. A fixed-effects analysis based on longitudinal data collected in 1998 and 2001 shows that social interactions on the subject of HIV/AIDS have significant and substantial effects on respondents' perceptions of the risk of HIV/AIDS, even after controlling for unobserved factors that affect the selection of social networks. These effects are more complex than previously thought. The dominant mechanisms--social learning and social influence--are found to vary by sex and by region, because of regional variations in the marriage pattern and the resulting implications for the formation of local social networks. The conclusion of the study is that rather than fostering denial and inaction, social interactions are an important vector of change in the face of the HIV/AIDS epidemic.