Forty-one patients with major depressive disorder were treated with electroconvulsive therapy (ECT). Sleep polysomnography studies (SPSs) were performed after the course of ECT. The hypotheses tested were that age is a significant factor in post-ECT SPS results and that some SPS parameters are correlates of outcome of ECT. An interaction between age and response to ECT could not be identified; however, older patients demon strated significantly disrupted sleep post-ECT. Response to ECT was associated with lower REM activity and lower REM density. Sleep-onset REM periods post-ECT were observed in almost 50% of the patients regardless of age. The SPS monitoring of recovery after a course of ECT may identify sleep correlates of response to ECT and variables associated with poorer longitudinal outcome.