 This is a randomized, double-blind, placebo-controlled, parallel-group, single site, 8-week trial of add-on ramelteon in outpatient adults 18-65 years old, inclusive with lifetime bipolar I disorder, with mild to moderate manic symptoms, and currently experiencing a clinically significant sleep disturbance. Approximately 60 subjects will be screened to obtain 30 subjects who enroll in the 8-week trial. Subjects will be randomized to ramelteon or placebo in a double-blind manner as add-on to current treatment. Any other psychotropic medications that the subject is taking at the initiation of participation in this protocol should be continued unchanged throughout the course of this study, except in instances in which these medications require dose reduction for management of side effects. Efficacy and safety assessments will be performed weekly, and the presence of treatment-emergent adverse events will be monitored and recorded. 