Choice of treatment schedule is an important component of the ongoing efforts to optimize electroconvulsive therapy (ECT) administration and thereby maximize therapeutic benefit while reducing cognitive adverse effects. Frequency of ECT administration (that is, the spacing between treatments) and the total number of treatments in a series are the two factors that define the ECT schedule. Available evidence supports the view that a schedule of twice weekly ECT with a total of six to eight treatments is an effective therapeutic regiment that potentially reduces cognitive morbidity associated with more frequent administration and a larger number of treatments. More frequent administration, however, may accelerate antidepressant response and may be indicated in cases in which rapidity of therapeutic effect is a significant clinical consideration. This consideration may be at the cost of greater cognitive impairment, which could be reduced by limiting the number of treatments administered. Aside from their clinical relevance, these issues have important implications for understanding the mechanisms of action of ECT.