There is limited information regarding the effectiveness of electroconvulsive therapy (ECT) as a treatment for patients in a mixed affective state. The authors report their experience using this treatment in medication-resistant patients meeting Research Diagnostic Criteria (RDC) for both mania and major depression. Clinical and response characteristics of these patients are described. Forty-one consecutively admitted patients meeting the RDC for mania received pharmacotherapy. Eight patients failing to respond to pharmacotherapy were referred for ECT, and seven consented. All met RDC for both mania and major depressive disorder. All patients receiving ECT remitted. The patient who did not accept ECT did not improve and ultimately needed transfer to a state hospital for longer term care. Mixed manic-depressive states are responsive to ECT, even in medication-refractory patients.