BACKGROUND: There is no effective treatment for chronic traumatic, ischemic, hypoxic, and anoxic brain injuries. We report the initial success of low pressure (LP) HBOT in their treatment. METHODS: All referrals with chronic stable encephalopathies manifested by perfusion/metabolism deficits on HMPAO SPECT scans that improved on repeat scan immediately after a 1. 5 or 1.75 ATA/90 min HBOT were included. Patients underwent 40(1), 60(1), or 80(16) HBOTs at primarily 1.5 ATA/90 mins q.d. or b.Ld. and standard rehabilitation when possible. Neurologic changes were noted by combinations of history, exam, video, occupational and physical therapists, neuropsychologists, referring doctors, and final SPECT scans. RESULTS: 18 pts (12 traumatic, 2 CVA, 2 anoxia, 1 hypoxia, 1 CP) were evaluated and treated. 18/18 showed motor, behavioral, personality, or cognitive gains. Baseline SPECT was 3.7 yrs (.2-15.2) post injury; rescan post O2 intervention was 22d (1-130) later. Final SPECT scans were performed within 2 weeks of final HBOT. All showed improvement over baseline SPECT. 6/18 patients noted neurological changes on the O2 intervention either in chamber or later that day. 16/18 noted neurological changes by 18 HBOTs (7-33) including emotional lability and personality changes. All noted changes by 40 HBOTs, many had further gains at 60-70, and all were improved at 80 HBOTs. 16/18 patients or their parents requested continuous treatment beyond the study endpoint of 80 HBOTs; 2 (40 and 60 HBOTs) stopped for personal reasons and sinusitis. CONCLUSION: Using SPECT brain imaging and LP HBOT living, non-functioning brain tissue can be identified, assessed for potential recovery (Neubauer-Gottlieb technique), treated, and neurorehabilitation achieved in the above encephalopathies. Clinical changes were reported as early as the first HBOT with neurological thresholds noted at 15-20, 40, and 60-80 HBOTs in many patients. 89% requested further treatment.