Review of the literature showed that anxiety commonly co-occurs with bipolar disorders (BDs), but the significance of such "co-morbidity" remains not clarified and its optimal treatment can not be adequately defined. Nearly half of BD patients meet diagnostic criteria for an anxiety disorder at some time. Such co-morbidity is associated with poor treatment reactions, substance abuse, invalidism. Prevalence of this co-morbidity appears to be greater among women than men, but similar in BD types I and II. Anxiety may be more likely in depressive phases of BD, but relationships of anxiety phenomena to particular phases of BD and their temporal distributions require clarification. Benzodiazepines are sometimes given empirically; antidepressants are employed cautiously to limit risks of mood switching and emotional destabilization; lamotrigine, valproate, and secondgeneration antipsychotics may be useful and relatively safe.