OBJECTIVE: The aim of this study was to assess the frequency of manic symptoms and bipolar spectrum disorders in an adolescent inpatient psychiatric sample using the Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS) Mania Rating Scale (MRS), parent and adolescent measures. METHOD: A total of 391 consecutive admissions to a psychiatric inpatient unit were assessed using the K-SADS MRS, the Childhood Inventory of Psychiatric Syndromes (CHIPS), and other clinically relevant measures. RESULTS: The frequency of Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) manic symptoms in this population was generally high. However, only 19.6% received a consensus diagnosis of juvenile bipolar disorder. The K-SADS MRS discriminated bipolar from non-bipolar patients when parents rated symptoms but not when rated by adolescents. CONCLUSIONS: This study of non-selected adolescents over a one-year period demonstrates that bipolar spectrum disorders in an inpatient population are common, and that the use of the KSADS MRS is effective in identifying this syndrome.