Research findings on effective teaching are being used to identify potential "master teachers." This paper discusses six problem areas with respect to using research results in this manner. The first problem area is the question of whether the concept of "master" is necessarily implied by the concept of "effectiveness." In effect, does knowledge of effective teaching practices provide a logical basis for making judgments regarding teaching mastery? A second problem is the matter of inferring unequivocally that teachers are causing higher or lower student achievement by their observed teaching behaviors and classroom processes. A third problem area pertains to the kind of student growth that researchers tend to investigate. Achievement measures employed in research on teaching often emphasize only the cognitive domain while overlooking the affective domain. A fourth question pertains to the generalizability of research confined to students of only one grade or level. A fifth problem area concerns the frequent assumption that relationships between teaching practice and student achievement are linear. The final problem area is that using the results of research on teaching for identifying master teachers is incongruous with the purpose of this research. (29 references) (JD)