OBJECTIVES: Low-frequency, right-sided repetitive transcranial magnetic stimulation (rTMS) to the prefrontal cortex has been shown to have antidepressant effects. Recent research has suggested that preceding low-frequency rTMS with a period of low-intensity, 6-Hz stimulation ("priming") enhances the physiological effects of low-frequency stimulation. The aim of this study was to investigate whether priming stimulation would enhance therapeutic response to low-frequency rTMS in patients with depression. METHOD: The study consisted of a 2-arm, double-blind, randomized, controlled trial in 60 patients with treatment-resistant depression. Right 1-Hz rTMS was provided in one continuous, 15-minute train to all subjects. The priming stimulation (twenty 5-second, 6-Hz trains) or an equivalent, sham preceded 1-Hz stimulation. The primary outcome variable was the score on the Montgomery-Asberg Depression Rating Scale (MADRS). RESULTS: There was a significant overall reduction in MADRS scores across the 4 weeks of the study and a significantly greater reduction in MADRS scores in the active-priming group compared with the sham-priming group. CONCLUSIONS: Low-intensity, high-frequency priming stimulation appears to enhance the response to low-frequency, right-sided rTMS treatment in patients with treatment-resistant depression.