Cisplatin (CP) is an effective chemotherapeutic agent used in the treatment of a variety of solid tumours. The most frequently observed side-effect of the use of CP is nephrotoxicity. Recently, evidence has been demonstrated that reactive oxygen species forming in the tubular epithelium play an important role in CP-linked nephrotoxicity. The aim of the study was to observe the effect of hyperbaric oxygen (HBO) therapy on CP nephrotoxicity, a subject which has not been studied previously. Wistar rats were treated with CP (a single intraperitoneal (IP) dose of 0.6 mg/100 g) alone and in combination with HBO (60 min every day for seven days at 2.5 x atmospheric pressure). Effects of the treatment on renal function and histology were determined. In analyses at the end of the study it was observed that serum urea, creatinine, and daily urinary protein excretion levels of the CP group were higher than at the start of the study, and that the creatinine clearance level had fallen (P < 0.05). There was no significant difference between the CP+HBO group and HBO group serum urea, creatinine, creatinine clearance, and daily urinary protein excretion levels at the beginning and end of the study (P > 0.05). Histopathological examination showed that the necrosis score in the proximal tubule epithelial cells and average apoptitic cell numbers in the CP group were higher than those in the CP+HBO and HBO groups (P < 0.05). There was no statistical difference between the CP+HBO group and the HBO group in terms of necrosis score in the proximal tubule epithelial cells and the percentage of distal tubules containing hyaline casts in the lumen. In conclusion, in this study it was observed that in experimental study of CP nephrotoxicity the synchronous application of HBO therapy with CP prevents kidney damage.