The clinical measurements of insight have focused primarily on patients' unawareness of their having a mental disorder and of their need for treatment ([Acta Psychiatr. Scand. 89 (1994) 62; Am. J. Psychiatry 150 (1993) 873]; etc.). A complementary approach focuses on some of the cognitive processes involved in patients' re-evaluation of their anomalous experiences and of their specific misinterpretations: distancing, objectivity, perspective, and self-correction. The Beck Cognitive Insight Scale (BCIS) was developed to evaluate patients' self-reflectiveness and their overconfidence in their interpretations of their experiences. A 15-item self-report questionnaire was subjected to a principle components analysis, yielding a 9-item self-reflectiveness subscale and a 6-item self-certainty subscale. A composite index of the BCIS reflecting cognitive insight was calculated by subtracting the score for the self-certainty scale from that of the self-reflectiveness scale. The scale demonstrated good convergent, discriminant, and construct validity: (a) the BCIS composite index showed a significant correlation with being aware of having a mental disorder on the Scale to Assess Unawareness of Mental Disorder (SUMD; Arch. Gen. Psychiatry 51 (1994) 826) and the self-reflectiveness subscale was significantly correlated with being aware of delusions on the SUMD, (b) the composite index score of the BCIS differentiated inpatients with psychotic diagnoses from inpatients without psychotic diagnoses, and (c) in a separate study, change scores on the BCIS were significantly correlated with change scores on positive and negative symptoms. The results provided tentative support for the validity of the BCIS. Suggestions were made for further investigation of the cognitive processes involved in identifying and correcting erroneous beliefs and misinterpretations.