A diagnostic classification of Borderline subgroups was developed for the purpose of reducing the current ambiguities existing in the range of pathologies between the psychoses and neuroses. This classification is a questionnaire of forty items and is intended to be used in treatment settings as a measure of object relations, i.e., of ego development and arrest. The criteria which define the Borderline subgroups were derived from the normative developmental data of Mahler, Pine, and Bergman (1975). In Experiment I, raters used the Mahler criteria as operational definitions of the developmental stages and sorted 180 items taken from Benjamin's structural Analysis Social Behavior (SASB) into the four Mahler substages. Those items which were reliably sorted eight out of nine times into the same Mahler stage or substage were retained as critical items to be administered in Experiment II to three groups of subjects. These groups consisted of nineteen schizophrenic inpatients, eighteen outpatients, and twenty nonpsychiatric volunteers. These subjects rated each item of the SASB questionnaire on a scale of 0 to 100; means for each type of psychiatric group according to sex were submitted to a repeated measures 2 (sex) X 3 (group) X 4 (Mahler substage) Analysis of Variance.