s / Brain Stimulation 8 (2015) 428e437 436 Methods: We implanted five adults with adjunctive bilateral EpCS over FP and ML prefrontal cortices. They had failed an average of 5.8 antidepressants prior to implant and were allowed to stay on medications and have changes as needed. All subjects received ongoing clinical assessments at baseline, seven-month (7mo), one-year (1yr), two-year (2yr), and five-year (5yr) time points. Results: All patients have continued to tolerate the therapy. The average improvements for all participants from pre-implant baseline on the Hamilton Rating Scale for Depression were [7mo] 54.9% ( 37.7), [1yr] 41.2% ( 36.6), [2yr] 53.8% ( 21.7), and [5yr] 45% ( 47). Three of five (60%) subjects continued to be in remission at 5yr. There were five serious adverse events: one paddle infection and four device malfunctions, all resulting in suicidal ideation and/or hospitalization with three involving the battery (2-drain, 1-turned off) and one involving connectors. Conclusions: This provides further evidence that chronic bilateral EpCS over FP and ML prefrontal cortices is a promising and potentially durable new technology for TRD. Supported By: NARSAD 2010 Independent Investigator grant.