Purpose: This paper aims to determine the knowledge that staff in day nurseries in Brazil had of basic measures to promote child health which are connected with high child mortality. These measures included breastfeeding, oral rehydration therapy, child growth follow-up, immunization and the identification of signs that indicate that the child must be referred to a health facility. Design/methodology/approach: A cross-sectional study was performed in day nurseries in the state of Bahia, Brazil, involving 194 care staff from 77 different establishments. Questionnaires, the observation of practical exercises and documentary evidence were used to assess knowledge. Findings: Seventeen percent of professionals were able to use growth charts correctly, 37.1 percent were able to prepare an oral rehydration solution adequately, 77.8 percent were able to provide appropriate breastfeeding counseling, 65.0 percent were able to identify children who showed respiratory danger signs and refer them to a health facility, and 58.5 percent were able to check the immunization status. This suggests a serious lack of basic knowledge in key areas. Research limitations/implications: The losses observed in the beginning of the study and the possibility of the existence of memory bias related to the verbal information obtained might have influenced the results. Practical implications: These findings suggest that there is an urgent need to address the lack of knowledge about basic child health measures shown by these key workers through appropriate educational programs. Originality/value: This is one of the first studies of levels of knowledge about basic child health measures in professionals who work outside the medical profession, and in particular in day nurseries. It also provides valuable information about health knowledge in a developing country. (Contains 2 tables.)