Reported are preliminary results from a randomized, double-blind study comparing the differential effects of unilateral-nondominant (UND) and bilateral (BL) electroconvulsive therapy (ECT) on memory function and clinical efficacy. The study included the serial administration (before, shortly after, and 6 months following a course of ECT) of behavioral ratings and memory tests for dominant and nondominant, anterograde and retrograde memory functions. Thus far, clinical improvement shortly after a course of ECT and 6 months later was significant for the entire sample and did not differ between the UND and BL groups. Most memory ratings worsened significantly after ECT, but returned to baseline levels 6 months later. Surprisingly, the scores generally did not differ between the UND and BL groups at any time point. Clinical implications for choice of administration are discussed.