This study was designed to investigate the convergent validity of individual clinical task interviews as presented by Piaget and Inhelder paired with three widely used group tests of cognitive development. These tests are designed to assess the acquisition of cognitive abilities. The three group test raw scores paired with summed raw scores on four concrete‐formal task interviews yielded the following Pearson product‐moment correlations: Reasoning Test (Ankney and Joyce), 0.43; Logical Reasoning Test (Burney), 0.61; Classroom Test of Formal Operations (Lawson), 0.37. The raw data was then ranked into cognitive level groups and presented on contingency tables. The following contingency coefficients were determined: Logical Reasoning Test, 0.52; Logical Reasoning Test (adjusted), 0.61; Classroom Test of Formal Operations, 0.50. This study reflects that the Reasoning Test tends to indicate lower cognitive levels of subjects when paired with summed scores on the clinical task interviews, whereas the Logical Reasoning Test and the Classroom Test of Formal Operations tend to indicate higher cognitive levels of subjects when paired with summed scores on the clinical task interviews. In each case the correlations do not appear to be sufficiently strong to warrant selection or categorization of an individual student based on his/her test performance.