A cross-sectional study of 354 children under two years of age was carried out in two periurban slums, with poor sanitary and socioeconomic conditions, located in Pelotas, southern Brazil. Most (79%) of the children studied were current users of pacifiers, 15% had never used one and the remaining 6% were ex-users. Among current users, 38% sucked a pacifier most of the time ("constant users"). Of the pacifiers in constant use, 93% were cultured for evidence of fecal contamination. Fecal coliforms were present in 49% of these. Diarrhoea was reported in 35% of all the children in the two weeks preceding the survey. Among constant pacifiers users, 40% had had diarrhoea in the preceding fortnight; this proportion was 32% for occasional users and 37% for non-users. These differences were not statistically significant.