The purpose of this research was to conduct a preliminary analysis of a new instrument designed to measure the psychological environment of the classroom. The instrument, the Classroom Environment Index (CEI), has been developed in an initial form. The structure was essentially the same as the other Syracuse Indexes (College Characteristics Index, High School Characteristics Index, etc.). It was based on Murray's Needs-Press model and contained 30 scales of 10 items each, totaling 300 items. The expectations of the present study was that the scales of the CEI would exhibit adequate discriminates among different classroom environments. Three forms of the CEI were administered to different samples. The following findings were reported: (1) The item discrimination indexes for the first two forms were adequate but somewhat lower than other Syracuse Indexes, while the discrimination indexes for the third form were considerably improved; (2) the reliability co-efficents were low in the first two forms, but considerably higher for the third form; (3) finally, it was found that the CEI scales differentiated between classrooms, subjects, grades, levels, and to some degree sexes. (Author/RK)