In a household survey in Bandim, Guinea-Bissau, 319 episodes of diarrhea in children of mean age 10.5 months were followed by interviews every second day of the episode until the mother reported that the diarrhea had stopped, the child was hospitalized, or 14 days had elapsed. Although most mothers knew about oral rehydration salts (ORS), only 58% of diarrhea episodes were treated with ORS and an inadequate amount was given to the child. Mothers who did not know about ORS failed to use it during the episode of diarrhea regardless of contact with a health center, suggesting that maternal knowledge is an important determinant of whether health personnel provide ORS. Children with diarrhea considered to be caused by teething were less likely to receive ORS during the acute phase. Univariate analysis found the use of ORS to be related to the number of reported symptoms, the mother being the caretaker, consultations, previous ORS use, good knowledge of ORS, and having ORS sachets at home. Multivariate Cox regression found the presence of ORS sachets at home at the onset of diarrhea to most strongly predict use. Improved health education should focus more upon the quantity of ORS needed, early signs of dehydration, the treatment of teething diarrhea, and breast-feeding, and reach out to mothers with no prior knowledge of ORS. Moreover, the management of diarrhea could be improved through the more liberal distribution of ORS sachets.