The staff of the Las Palmas School for Girls expressed a desire for a system other than psychiatric diagnosis for assigning girls to differential treatment modalities. TheInterpersonal Maturity Levelsystem was incorporated into the classification procedures of the institution and was found to be pragmatically useful. The major advantage of the system is that it suggests staff styles, treatment modalities, and etiological aspects oftypesof delinquents based upon perception and behavior. An effort was made to objectify the identification of I-Level types through a Q-factor analysis of a psychological inventory. The attempt failed; however, the Q-analysis helped uncover covert manipulators early in the institutionalization process and appeared to be a step forward in the development of an objective, general typological system.