The aim of the present study is to evaluate role of plasma antioxidants (albumin, bilirubin and uric acid) in patients suffering from type I Bipolar Disorder (BD-I) during different phases of illness: acute mania, euthymia and bipolar depression. Medical records of consecutive 110 BD-I patients (38 patients with acute mania, 35 in euthymic state, full remission, and 37 in depressive phase) were reviewed to evaluate plasma antioxidant levels. Laboratory data of 40 healthy controls were also obtained. The scores of Young Mania Rating Scale (YMRS), Bech-Rafaelsen Manic Rating Scale (BRMRS) and Hamilton Rating Scale for Depression (HAM-D) were evaluated. Serum uric acid levels were higher in acute mania than other patient subgroups and healthy controls. Serum uric acid levels directly correlated with BRMRS and YMRS scores. No differences were found between clinical groups during different phases and healthy controls concerning albumin and bilirubin. In conclusion, the results of the present study support the notion that serum uric acid levels may be higher in patients with BP-I (especially during manic phases) which may suggest a dysregulation of the purinergic system. However, limitations should be considered and further studies are needed.