A set of "tests of scientific thinking" were developed for possible use as criterion measures in research on creativity. Scores on the tests describe both quality and quantity of ideas produced in formulating hypotheses, evaluating proposals, solving methodological problems, and devising methods for measuring constructs. The tests were administered to 3,500 candidates for admission to graduate school in psychology, using an item-sampling procedure. Correlations with GRE scores were low, especially for scores based on number of ideas. Follow-up questionnaires were sent to students asking for information about graduate school attendance, grades, accomplishments during the first year of graduate study, and self-appraisals of professional skills. Scores based on quantity (number of responses, number of unusual responses, and number of unusual responses that were also of high quality) were significantly related to self-appraisals and to reports of such professional accomplishments as collaborating in research, publishing scientific papers, and designing and maintaining research apparatus. The quantity scores also were related to indices reflecting the quality of the department attended and to conventional evaluations of student performance. GRE scores were better at predicting these indices of quality but poorer as predictors of accomplishments and self-appraisals.