The purpose of this study was to estimate the effects of ribose supplementation on interval anaerobic performance and fatiguing substance concentrations. The study cohort consisted of physically active, young male volunteers (n = 15). With a double-blind cross over study design, each participant completed two all-out anaerobic exercise sessions, one week apart, one by supplementing maltodextrine and the other by supplementing ribose (150 mg/kg in each test). Two repetitions of 30-s maximal performance with a 4-min interval were completed. Blood samples were taken at rest and five minutes after the second sprint repetition. Neither the biochemical parameters: pH (-0.32 +/- 0.09 vs. -0.26 +/- 0.11), lactate (La) (13.8 +/- 1.9 vs. 13.3 +/- 2.7 mM, ammonia (423 +/- 190 vs. 404 +/- 166 mu mol/L), inorganic phosphate (Pi) (0.68 +/- 0.53 vs. 0.72 +/- 0.63 mM) nor the anaerobic output (746.2 +/- 82.5 vs. 760.2 +/- 86.8 watts) were affected by placebo and ribose supplementations significantly (p > 0.05). In conclusion, based on this protocol, anaerobic performance and/or biochemical status are not affected by ribose supplementation.