A recreational scuba diver with nervous system decompression illness had a poor response to hyperbaric therapy. On the basis of available and supportive in vivo data, he was then given a continuous infusion of lidocaine (serum levels, low therapeutic range: 6.4-9.1 mumol/liter). Within 24 h of the start of this infusion he experienced a full resolution of his neurologic deficits. His symptoms recurred 3 days later, but again completely resolved after further hyperbaric therapy and concurrent administration of lidocaine (serum levels: 6.9-9.1 mumol/liter). This observation supports the need to conduct trials of lidocaine as an adjunct to hyperbaric therapy in decompression illness.