Although pacifiers are commonly used by Brazilian children and are potencially harmful, there are no studies about their patterns and determinants. These were investigated in a cross-sectional study of 354 children under two years of age living in two slum areas of Pelotas, southern Brazil. Most children (79%) were pacifiers users, 15% had never used them, and 6% had used them in the past. Among users, 38% spent most of the time sucking a pacifier. For two-thirds of the children, pacifiers were ofered on the very first day of life. Pacifier use was most common among younger children, among those of low-schooling mothers and among nonbreastfeed infants.