Examined causal reasoning about AIDS in children representing three major phases of cognitive development: prelogical, concrete logical, and formal logical thinking. 60 Ss (age groups: 5-7 years, 8-10 years, and 11-13 years) were administered the Concepts of AIDS Protocol. Responses were scored using the developmentally ordered Concepts of Illness Category System. The data confirm that, as a group, children's causal thinking about AIDS parallels the ways in which children think about illness in general. More specifically, the data could be organized in terms of 6 major categories or ways in which children conceptualize AIDS and its causes. The findings provide an initial empirical foundation for AIDS education curricula.