Background. Systematic and accurate depiction of a patient's course of illness is crucial for assessing the efficacy of maintenance treatments for bipolar disorder. This need to rate the long-term prospective course of illness led to the development of the National Institute of Mental Health prospective Life Chart Methodology (NIMH-LCM^TM-p or LCM). The NIMH-LCM^TM-p allows for the daily assessment of mood and episode severity based on the degree of mood associated functional impairment. We have previously presented preliminary evidence of the reliability and validity of the LCM, and its utility in clinical trials. This study is a further and more extensive validation of the clinician rated NIMH-LCM^TM-p.Methods. Subjects included 270 bipolar patients from the five sites participating in the Stanley Foundation Bipolar Network. Daily prospective LCM ratings on the clinician form were initiated upon entry, in addition to at least monthly ratings with the Inventory of Depressive Symptomatology-clinician rated (IDS-C), the Young Mania Rating Scale (YMRS) and the Global Assessment of Functioning (GAF). We correlated appropriate measures and time domains of the LCM with the IDS-C, YMRS and GAF.Results. Severity of depression on the LCM and on the IDS-C were highly correlated in 270 patients (r = −0·785, P < 0·001). Similarly, a strong correlation was found between LCM mania and the YMRS (r = 0·656, P < 0·001) and between the LCM average severity of illness and the GAF (r = −0·732, P < 0·001).Conclusions. These data further demonstrate the validity and potential utility of the NIMH- LCM^TM-p for the detailed daily longitudinal assessment of manic and depressive severity and course, and response to treatment.