Lidocaine is the most extensively studied substance for adjuvant therapy in neurological decompression illness (DCI), but results have been conflicting. In this retrospective cohort study, we compared 14 patients who received adjuvant intravenous lidocaine for neurological decompression sickness and cerebral arterial gas embolism between 2001 and 2011 against 21 patients who were treated between 1996 and 2001 and did not receive lidocaine. All patients were treated with hyperbaric oxygen (HBO2) therapy according to accepted guidelines. Groups were comparable for all investigated confounding factors, except that significantly more control patients had made an unsafe dive (62% vs. 14%, p = 0.007). Groups had comparable injury severity as measured by Dick and Massey score (lidocaine 2.7 +/- 1.7, control 2.0 +/- 1.6), an adapted version of the Dick and Massey score, and the Blatteau score. Number of HBO2 sessions given was comparable in both groups (lidocaine 2.7 +/- 2.3, control 2.0 +/- 1.0). There was neither a positive nor a negative effect of lidocaine on outcome (relative risk for objective neurological signs at follow-up in the lidocaine group was 1.8, 95% CI 0.2-16). This is the first retrospective cohort study of lidocaine in neurological DCI. Since our study is under-powered to draw definitive conclusions, a prospective multicenter study remains the only way to reliably determine the effect of lidocaine in neurological decompression illness.