This article reports findings from a study of how early childhood teachers think about and use child observation in Australian and US classrooms. Qualitative research methods were used to collect and analyse data from the two nations, and the paper reports on how teachers use child observation in each country. Uses in US early child settings included: assessing academic progress, adjusting curriculum/teaching strategies, diagnosing instructional needs/readiness, gathering information for reports to parents, dealing with behaviour problems, assessing social adjustments, and documenting special needs. Australian uses included: identifying individual strengths and weaknesses, understanding children to guide their behaviour, informing work with parents and other professionals, extending shared interests among children, noting individual differences that can extend the learning of the group, reflecting on the flow of the day, and evaluating teaching. Research methods are described, similarities and differences across data sets are discussed, and implications for policy and practice are presented.