Direct costs of college instruction were assessed by type of institution and type of instructional program (i.e., by discipline). Determining direct costs by level of instruction involves allocation procedures focusing on faculty time. Central tendencies were derived from the results of a large number of studies. Data sources included reports of state coordinating or governing boards, institutional research studies and dissertation research, and studies conducted by the National Center for Higher Education Management Systems. There are systematic differences in cost ratios per credit hour by type of institution (i.e., baccalaureate, comprehensive, doctoral, research, and doctoral and research). With a few exceptions, the larger and more complex the institution, the larger the cost ratios. In considering differences by discipline and institution, comprehensive institutions had relatively high cost ratios in the sciences, both national and social. This occurred when comparing upper- to lower-division levels as well as masters to lower division. Very low costs at the lower-division level for mathematics and the social sciences, and relatively high costs at the upper-division level for the laboratory-oriented sciences, were found at both doctoral and comprehensive institutions. Six pages of references conclude the report. (SW)