The literature reflects that brief pulse electroconvulsive therapy (ECT) uses less energy to elicit seizures and produces less cognitive disturbance than does sine wave ECT. However, the relative effectiveness and efficiency of the two waveforms have not been firmly established. In an effort to clarify these issues, the authors retrospectively compared a diagnostically heterogeneous group of 197 patients who received sine wave ECT with a similar group of 144 patients who received brief pulse ECT. The average number of ECT treatments administered to each group was essentially the same. Among a more homogeneous group of patients with affective disorders treated with either bilateral or mixed electrode placements, the number of treatments required with each waveform did not differ significantly.