The phenomenology of the manic state and its response to lithium drug treatment were intensively studied as part of a larger NIMH Clinical Research Branch Collaborative Program on the Psychobiology of Depression. In view of the weaknesses in current methods for measuring the components of the manic state, a new instrument was developed, the Manic Diagnostic and Severity Scale (MADS). Its sensitivity in diagnosis and in measuring change was compared to other scales already in use. Finally baseline clinical data is presented that suggests that the presence of a "mixed" manic state is a predictor of lack of clinical response to lithium treatment.