AbstractIn view of the absence of a unitary definition of schizophrenic thinking, and, consequently, of a single, objective diagnostic technique for its measurement, it was decided to study the relative effectiveness of a number of highly structured (objective) testing procedures that are accepted clinically as possessing some validity in the detection of such thinking. Five generally used, objective tests of schizophrenic thinking (Whitaker Index of Schizophrenic Thinking, Shipley‐Hartford Intelligence Scale, Gorham Proverbs Test, Goldstein‐Scheerer Object Sorting Test, and the Similarities and Comprehension subtests of the Wechsler Adult Intelligence Scale) were administered to 36 nonschizophrenic and 23 schizophrenic patients (as classified by the New Haven Schizophrenic Index). Results indicated that despite greater intratest correlations, moderate relationships were found among three of the five techniques, indepedent of whether they measured general or specific deficit, active or passive thinking, and/or positive or negative symptoms. Discriminant analysis indicated that the most accurate and economical combinations of techniques in the differential diagnosis of schizophrenic thinking, for a homogeneous, mildly to moderately impaired hospital population, would be a combination of a measure of generalized deficit and a measure of positive sympt