Pediatricians provide a major source of knowledge for parents about children's behavior and development, although their advice is largely based on their own cultural values and beliefs in interaction with their personal and clinical experience. This review presents cross-cultural aspects of children's sleep behavior in industrialized and complex modern societies and provides a basis for understanding dimensions and mechanisms of cultural differences. We submit that it is the interaction between culture and biology that establishes behavioral and developmental norms and expectations regarding normal and problematic children's sleep. Pediatricians need to recognize the cultural environment in which children live and be knowledgeable about how cultural beliefs and values of both families and physicians interact with the needs and biological characteristics of individual children.