The Purdue Interest Questionnaire (PIQ), a 264-item Likert-type scale, was developed to assist engineering students in their career planning. The six engineering scales identify specialized fields: aeronautical, chemical, civil, electrical, industrial, or mechanical. For students planning to transfer out of engineering, four scales identify interest in other fields: humanities and social science, industrial management, science and mathematics, and engineering technology. Two scales measure general educational orientation--for students most likely to persist in engineering, to transfer, or to withdraw from college. The scales were developed in 1966 by analyzing existing interest inventories, and by comparing the responses of 99 freshman engineering students with selected groups of other freshman engineering students. The PIQ has some limitations--it is not an ability or achievement measure, and few women participated in its development. Scores are compared both against scores of freshman engineers in general, and against ten mutually exclusive groups--those persisting and those transferring from the field. Although test-retest reliability coefficients of some scales are low, they are all significant. Discriminant function classification of students, based upon their PIQ scale scores, produces significant percentages of correct classification beyond chance--thus demonstrating PIQ validity. (CP)