In this paper, we explore the diffusion of beliefs pertaining to the causes of childhood diarrhea in rural Guatemala. The analysis focuses on the importance of interpersonal and impersonal contacts as conduits for information and norms related to hygiene and contamination. Estimates from multivariate models reveal that there is evidence of a diffusion process through social contacts, primarily through interpersonal ones. The analysis also identifies striking differences between (1) the diffusion process related to hygiene (e.g. dirtiness) and that related to contamination (e.g. pathogens); and (2) beliefs about the causes of diarrheal illness among children in general and those among respondents' own children.