Recent research suggests that there may be systematic differences in instruction and learning associated with particular social studies subjects. The researchers question whether social studies instruction differs across the various subjects that constitute the social studies curriculum. If so, to what extent do these differences have educationally significant consequences? Social studies curriculum planning involves, whether consciously or not, a classification of subjects. The examination of social studies courses suggests that boundaries vary, between these subjects, from strong to weak, with the weaker boundaries in the middle and elementary-school grades. There is some evidence that teachers' conceptions of a particular subject affects how they interpret the goals of the curriculum and which instructional strategies they employ. A review of the research literature found that the choices of curricular organization and instructional strategy influence what is learned, how it is learned, and what counts as evaluation. I. L. Beck and M. G. McKeown (1989) concluded that the social studies curriculum has been too global and vague to allow a meaningful understanding of instructional practices. A 33-item bibliography is appended. (NL)