35 patients with chronic, nonspecific low back pain were randomized in this exploratory trial to the addition of either active or sham transcranial direct current stimulation (tDCS) sessions prior to starting a group exercise program for 1 month. The tDCS sessions were completed over 5 consecutive days prior to group exercise intervention. Patients were assessed primarily for pain response during and after tDCS intervention, following completion of the group exercise program, and at 1-month follow-up. Within-group reductions in visual analog scale (VAS) pain score after each tDCS session were significant in the active tDCS group, but not in the sham tDCS group. Overall reduction in pain from baseline to 1-month follow-up was also significantly greater in the active tDCS group compared to the sham tDCS group, as was the rate of responders (ie. minimum 30% reduction in VAS). Most common adverse events in both groups were skin redness and tingling.