In Piaget's developmental psychology the fourth and highest stage of human cognitive development is that of formal operations. The research on formal thought instruments is outlined. This study was designed to construct and validate paper-and-pencil instruments which could be used to select students capable of abstract conceptualization, hypothetico-deductive thought, and combinational reasoning. Three tests in different content areas were developed using item specifications found in the Piagetian literature on formal operations. Items were six-choice logic items with abstruse content. These tests, four Piagetian formal thought tasks, and a measure of verbal intelligence were administered to a sample of above-average teenagers. The formal operational reasoning tests were demonstrated to have substantial content validity, modest concurrent validity, and limited construct validity. Six item structures were found to have uniformly high first principal component factor loadings, validity indices, and reliability indices. The need for further research in this area is pointed out. (DG)