Cholesterol interacts with serotonin and it has been found to be associated with some clinical symptoms of mood disorders. There is a paucity of data on first-onset bipolar patients and from Asian population. The total cholesterol (TC) level was examined in 25 bipolar I patients with a single manic episode (BPSM) and 30 controls. The TC level was significantly lower in the BPSM than in the controls. There were negative correlations between the Young mania rating scale (YMRS) scores and the pretreatment TC level in BPSM. This study suggests that the TC level can be changed after treatment in bipolar manic patients, although more studies involving different ethnic groups will be needed.