Almost all studies of the open classroom are phenomenological. The purpose of this investigation was to determine quantitatively the effects of open and traditional classroom techniques on teacher and student interaction and social environment. The ETS instrument, PROSE (Personal Record of School Experience), was utilized by observers to measure directly in public classrooms, on a time-sampling basis, selected traits attributed to open classrooms by prominent writers. The one-tail t-test was used to compare mean frequencies on each trait for open vs. traditional classrooms. Analysis of data revealed the open classrooms to be significantly different from traditional classrooms, as predicted. The study also demonstrated that quantitative methods can be applied to the open classroom to achieve operational definitions which can be further researched.