Obesity is highly prevalent in persons with bipolar disorder. This results in increased physical morbidity and poorer psychiatric outcomes. Multiple variables have been identified as potentially responsible for the weight gain in these individuals. Efforts to use successful treatment strategies require an understanding of these variables and methods that clinicians and their clients can use to reduce or minimize these risk factors. This article will review the emerging findings related to primary and secondary weight gain in bipolar disorder. The sequelae of weight gain on psychiatric and medical morbidity will be discussed. Lastly, a model for nursing assessment will propose methods for modifying risk factors and encouraging healthy lifestyle changes. The goal is to improve this component of quality of life for persons with bipolar disorder. J Am Psychiatr Nurses Assoc, 2008; 13(6), 345-352. DOI: 10.1177/1078390307310145.