Recently, a 52-item self-report questionnaire, called the Borderline Syndrome Index (BSI), was developed to provide a rapid clinical assessment of the borderline syndrome (Conte, H. R., Plutchik, R., Karasu, T. B., and Jerrett, I. A self-report borderline scale: Discriminative validity and preliminary norms. J. Nerv. Ment. Dis., 168: 428-435, 1980). The present investigation addresses the question of the applicability of this test instrument over the full range of borderline syndrome psychopathology, as defined by DSM-III diagnostic criteria, as well as the relationship of various demographic, treatment, and personality variables to total scale scores. The final sample consisted of 51 patients meeting DSM-III diagnostic criteria for borderline personality disorder, 14 patients with DSM-III defined schizotypal personality disorder, 17 patients meeting DSM-III diagnostic criteria for borderline and schizotypal personality disorder, 30 CATEGO-defined early schizophrenics (first psychotic episode within the past 2 years), and 20 normal control subjects. All patient groups scored significantly higher than the normal group on the BSI, and each borderline syndrome group was discriminable from the early schizophrenic group but not from each other. None of the demographic variables correlated significantly with BSI total scores. Treatment variables were somewhat related to total scores, and it is suggested that chronicity rather than severity of disturbance may strongly affect performance on the BSI. Principal component analysis of BSI items, as well as high correlations between scores on the BSI and almost every scale on the MMPI, suggests that the BSI may be tapping a general, rather than specific, dimension of psychopathology. This dimension might best be described as a generalized deficiency in coping with life, with resultant feelings of hopelessness and worthlessness. While the present study provides some support for the discriminative validity of the measure, further evidence for the validity of the BSI as a specific measure of borderline syndrome psychopathology is clearly indicated before its widespread implementation.