During 12 months, 26 households with 172 residents in São Felipe, Bahia, Brazil, entertained 74 different guests who were potentially exposed to attack by Panstrongylus megistus for an average of about 23 nights per guest per year. During the same period 52 of the residents spent an average of about two weeks a year away from home. These exchanges established contact with 79 other households in the district. These and other observations reinforce the opinion that human behaviour plays an important role in propagating Chagas' disease.