This research tested the validity of the prevalent assumption that a teacher's conception of the nature of science influences his/her classroom behavior. The subjects consisted of 18 senior high school biology teachers and one randomly selected tenth-grade biology class of each teacher. Each class (mean size of 22.72 students) was heterogeneous with respect to sex, race, and socioeconomic status. Teachers were compared with respect to their conceptions of six aspects of the nature of science (amoral, creative, tentative, testable, parsimonious, and unified) as measured by the Nature of Scientific Knowledge Scale (NSKS). Quantitative comparisons were made between "high" teachers (those exhibiting the highest NSKS scores) and "low" teachers (those exhibiting the lowest NSKS scores) with respect to 44 classroom variables. Only one variable differentiated between the "high" and "low" groups of teachers. Thus the data did not support the prevalent assumption that a teacher's conception of the nature of science influences his/her classroom behavior. Interestingly, most of the classroom variables used for teacher comparisons have previously been shown to be related to improved student conceptions of the nature of science. (Author/JN)