OBJECTIVE To examine the association between treatment adherence and indirect productivity costs within a cohort of commercially insured employees with bipolar disorder in the United States. METHODS Adults diagnosed with bipolar disorder who had at least one prescription claim for a mood stabilizer or atypical antipsychotic, with 6 months prior and 12 months subsequent continuous medical and prescription coverage, were identified in the MarketScan research databases (2000-2005). Two-part multiple regression models estimated the association between adherence (medication possession ratio > or =0.80) and costs of absence, short-term disability, and workers' compensation. RESULTS Of 1258 eligible employees, only 35.3% were adherent. Relative to adherent employees, nonadherent employees had higher adjusted indirect costs due to absence (+$771.41), short-term disability (+$284.72), and workers' compensation (+$360.63). CONCLUSIONS Employers incur greater indirect costs when employees are not adherent to bipolar treatment.