Risperidone has been shown to be effective in controlling symptoms of acute mania or mixed state in two registration monotherapy and one combination treatment study with lithium or valproate, as well as several smaller trials. However, longer-term treatment studies are relatively lacking. As well, although Risperdal Consta(TM) has been shown to be of benefit in prevention of relapse in patients with schizophrenia, relatively little longer-term data in bipolar disorder is available. Nonetheless, both risperidone and Risperdal Consta (TM) are likely to be highly efficacious for the maintenance prevention of relapse in bipolar disorder. Moreover, Risperdal Consta(TM) helps to ensure longer-term treatment effectiveness, both by better adherence and improved control of symptoms. The present study is intended to determine whether Risperdal Consta(TM) injections, added to ongoing pharmacotherapy, will improve outcome relative to treatment as usual.