The results of this study empirically demonstrate the importance of cross-validating an instrument intended for use in a future study. The instrument used was the Teachers' Practices Questionnaire (TPQ) which had been devised in 1963 to measure teachers' subjective role expectations. Three samples of undergraduate and graduate students who were, at the time of data collection, attending schools of education were employed in the study. Results from the first of these samples, analyzed to determine the extent of the invariance of the factorial structure of responses to the TPQ, revealed that two of the six roles proposed by the authors of the original 120-item instrument disappeared. In a revised TPQ, consisting of 28 items, four factors (Counselor, Motivator, Referrer, and Disciplinarian) emerged from the factor analysis, but the intercorrelations were judged to be too low to be psychometrically valid. Additional revisions and the addition of items clearly delineated the four role factors and, with one exception, each item was positively correlated with its appropriate factor and no other. A copy of the final 40-item version of the TPQ and a factor analysis are included. See TM 000 401 for a review of the instrument. (TA)