Decompression illness (DCI) is due to bubble formation in the blood or tissues following the breathing of compressed gas. Clinically, DCI may range from a trivial illness to loss of consciousness, death or paralysis. Recompression is the universally accepted standard for the treatment of DCI. When recompression is delayed, a number of strategies have been suggested in order to improve the outcome.To examine the effectiveness and safety of both recompression and adjunctive therapies in the treatment of DCI.We searched CENTRAL (The Cochrane Library 2005, Issue 2); MEDLINE (1966 to August 2005); CINAHL (1982 to August 2005); EMBASE (1980 to August 2005); the Database of Randomised Controlled Trials in Hyperbaric Medicine (August 2005), and hand-searched journals and texts.We included randomized controlled trials that compared the effect of any recompression schedule or adjunctive therapy with a standard recompression schedule. We applied no language restrictions.Three authors extracted the data independently. We assessed each trial for internal validity and resolved differences by discussion. Data was entered into RevMan 4.2.Two randomized controlled trials satisfied the inclusion criteria. Pooling of data was not possible. In one study there was no evidence of improved effectiveness with the addition of a non-steroidal anti-inflammatory drug (tenoxicam) to routine recompression therapy (at six weeks: relative risk (RR) 1.04, 95% confidence interval (CI) 0.90 to 1.20, P = 0.58) but there was a reduction in the number of compressions required when tenoxicam was added (P = 0.01, 95% CI 0 to 1). In the other study, the odds of multiple recompressions was lower with a helium and oxygen (heliox) table compared to an oxygen treatment table (RR 0.56, 95% CI 0.31 to 1.00, P = 0.05).Recompression therapy is standard for the treatment of DCI, but there is no randomized controlled trial evidence. Both the addition of an NSAID or the use of heliox may reduce the number of recompressions required, but neither improves the odds of recovery. The application of either of these strategies may be justified. The modest number of patients studied demands a cautious interpretation. Benefits may be largely economic and an economic analysis should be undertaken. There is a case for large randomized trials of high methodological rigour in order to define any benefit from the use of different breathing gases and pressure profiles during recompression therapy.