OBJECTIVES: The Netherlands Mental Health Survey and Incidence Study (NEMESIS) is a prospective survey in the Dutch general population among 7.067 respondents aged 18 to 64. In a follow-up study on the prevalence of bipolar disorder (BD) respondents were identified by using the the Structured Clinical Interview (SCID) resulting in a DSM-IV diagnosis for BD. The objective was to explore the costs to society of BD in the Netherlands. All available 40 persons identified with a life-time diagnosis of BD(DSM-IV) were interviewed. Detailed data on medical health care utilisation (direct costs) and production losses due to absence from work and efficiency losses (indirect costs) as well as quality of life was collected. METHODS: We used the 'Trimbos and iMTA questionnaire on Costs associated with Psychiatric illness (TiC-P). The TiC-P includes a short version of the Health and Labour questionnaire (HLQ) for collecting data on lost productivity and efficiency losses. For the quality of life we applied validated generic instruments; the EQ5D of the EuroQol group and the Short-form 36. RESULTS: The average direct costs per patient per year was estimated at €897 (range: 0-3200). The average indirect costs per year was €3720 (range: 0-6373) of which 86% was due to absence from work. The average score on the EQ5D was 0.82 (sd 0.2).The quality of life was not significantly lower for the BD population compared to the general population (0.87). Based on the prevalence of 5.2% the total costs of bipolar disorder were estimated at €1.93 billion (total direct costs = €480 million; total indirect costs = €1.45 billion). CONLCUSIONS: The societal costs for bipolar disorder in the Netherlands are high, especially the indirect costs due to absence from work. Adequate treatment of bipolar disorder could help reduce the societal costs and improve patients' quality of life.