We tested and compared the use of two adjunctive hormonal agents, tamoxifen and medroxyprogesterone acetate (MPA), for the treatment of acute mania or hypomania. A total of 13 women with acute Bipolar Affective Disorder in the manic or hypomanic phase were recruited from a clinical population to participate in this 28-day, three-arm, double blind, placebo-controlled study. The women who received tamoxifen exhibited significant improvement in symptoms of mania from baseline to final assessment compared with the placebo group. The MPA group improved more than the placebo group. Further exploration of tamoxifen as a useful adjunct in the treatment of acute manic symptoms in women with Bipolar Affective Disorder is warranted.