Bipolar disorder is a recurrent lifelong illness. Lithium is still the drug of first choice in the prophylactic treatment. However, lithium’s side effects are considerable. Thus the interest in developing alternatives to lithium has increased, and various antiepileptic drugs have been studied. Among these, lamotrigine, which generally is well tolerated, has been evaluated in industry generated trials. However, for various reasons, the generalisability of the results from these studies is limited. Also the follow-up time is limited. This study is a pragmatic effectiveness study, overcoming some of these limitations, and comparing lamotrigine with that of lithium in terms of their potentials for preventing new episodes in patients with bipolar disorder.