The aim of the present study was to test the hypothesis that a brief clinical test of frontal lobe system (FLS) maturity levels, designated as Stages I, II, III, IV, can differentiate between three experimental groups (all of age 9-16): normal Ss, Ss with emotional problems, and juvenile delinquents. The stages represent 1) disjointedness of activities; 2) inability to switch the principle of action of an ongoing activity appropriately; 3) planning, and 4) ability to switch the principle of action of an ongoing activity and to re-program it appropriately in accordance with new circumstances. By means of a blindly performed brief form analysis of action patterns expressed through narratives, it was shown that 70% of the normal Ss attained stage IV, but only 47% of the delinquent Ss did so. These findings support the previously proposed new conceptual model about ethical action behavior in general (Pontius, 1972) and in particular with regard to a subgroup of juvenile delinquents who reveal signs of a neuro-physiological dysfunction, probably a maturational lag of the FLS. In the present sample, this appears to be especially revealed in the specific inability to switch in a flexible manner the principle or plan of action of an ongoing activity according to new circumstances, resorting to re-programming. Such specific inability calls for specific classification as such, thereby enabling the formulation of specific remedial efforts, which are discussed.