The concurrent validity of interview-based ratings of negative symptoms in 35 inpatients with chronic, treatment refractory schizophrenia was evaluated. Correlations were examined between interview-based ratings of negative symptoms, measured by the Brief Psychiatric Rating Scale and the Positive and Negative Syndrome Scale, and the naturalistic behavior of inpatients as assessed by the Time Sample Behavior Checklist. Higher levels of interview-based negative symptoms were related to reduced interpersonal activity on the inpatient ward, but not to entertainment, instrumental or self-maintenance activities. These findings offer partial support for the concurrent validity of office-based ratings of negative symptoms, and highlight the importance of longitudinal observations of patients for accurate identification of negative symptoms.