Background: The electrical dose selected for electroconvulsive therapy (ECT) must have an acceptable efficacy and no or minimal cognitive side-effects. We evaluated the clinical efficacy and cognitive side-effects of ECT in relation to the stimulus dose administered. Method: This study assessed 71 depressed patients who were treated with bilateral ECT. For evaluation of depressive and cognitive states the mini-mental state examination (MMSE) and Hamilton scale for depression (HAM-D) were used before starting ECT and after the fourth and last sessions. Results: The baseline mean MMSE was significantly (p=0.005) different with that evaluated after the fourth (p=0.005) and the final (p=0.002) sessions among the four groups receiving various doses of ECT. The mean Hamilton score did not change significantly over the study. No decrease in cognition was observed with employing higher doses (224–345.6 mc) of ECT compared to lower doses. The rate of improvement did not change significantly among the studied groups. Conclusion: Cognitive function does not decreased with higher doses of ECT (224–345.6 mc) as compared to the other groups. The rate of improvement does not differ with the stimulus dose administered.