This paper evaluates the quality of the data collected as part of the Kenya and Malawi Diffusion and Ideational Change Projects, two longitudinal household surveys that examine the role of social networks in attitude formation and behavior regarding family planning, and HIV/AIDS in rural Kenya and Malawi. We investigate three sources of non-sampling error: interviewer effects, response unreliability and sample attrition, and discuss their possible interactions. We pay particular attention to their implications for AIDS-related behavioral research.