This study investigates age differences in children's semantic expectations regarding causal relations in stories about three realistic goal situations (being friendly, getting a dog, and doing chores). Twenty children at each of three age levels (ages 6, 9, and 12) were asked to produce stories and answer probe questions about wanting and not wanting to be friendly, to get a dog and to do chores. The probe questions focused on three types of causal relations: motives, means and obstacles. Each child was interviewed individually and sessions lasted approximately 45 minutes. A taxonomy of plausible categories of information about goal situations was developed to score the protocols. The general conclusion was: developmental changes in semantic knowledge systems for realistic goals are associated primarily with the kinds of semantic information in the knowledge base, rather than with the structure of the knowledge base. That is, if particular information was in the knowledge base, the type of causal relation associated with the information was similar across ages. In addition, "core categories" were distinguished for each age group (categories which were mentioned by at least 90% of the children in a particular age group). The Core knowledge base data indicated the presence of both developmental similarities and differences, depending on the goal situation. In general, the Core knowledge base for the older children included the same information as that of the younger children plus additional information. (Author/SS)