BACKGROUND: It has been suggested that electroconvulsive therapy (ECT) with an ultra-brief pulse width in combination with a bilateral electrode placement has diminished antidepressive efficacy, as compared to unilateral ultra-brief pulse ECT. OBJECTIVE: The antidepressive efficacy of bifrontal and right unilateral ultra-brief pulse (0.3 ms) ECT were compared. METHOD: Eighty-one patients with a medication refractory depressive episode were treated with a course of bifrontal ultra-brief pulse ECT at 1.5 times seizure threshold or unilateral ultra-brief pulse ECT at 6 times seizure threshold by random assignment. The 17 item-Hamilton Rating Scale for Depression (HRSD), Beck Depression Inventory, Clinical Global Impression and Patient Global Impression were administered at baseline and repeated weekly during and 1 and 6 weeks after the course, by a blinded rater. RESULTS: 64/81 patients (79%) completed the study, half of which were treated with bifrontal ECT. At the end of the course, 78.1% of the BF group and 78.1% of the UL group responded, whereas, 34.38% (N=11) of the BF group and 43.75% (N=14) of the UL group achieved strict remission criteria (HRSD-score < or = 7). There were no significant differences between the patients given bifrontal ECT and those given unilateral ECT, although patients receiving unilateral ECT achieved response/remission-criteria after a smaller number of treatments. LIMITATIONS: Relatively small number of subjects. CONCLUSIONS: Using an ultra-brief pulse width, both BF and UL-ECT are efficacious, although patients receiving UL-ECT achieve response/remission-criteria after a smaller number of treatments. Trial registry: http://www.controlled-trials.com/ Registration number: ISRCTN56570426.