Oxygen free radicals are produced during stress, are unstable, and potentially interact with other cellular components or molecules. This reactivity can influence cellular function, including a prolongation in tissue recovery following exercise. We tested the effect of ribose (d-ribose), a pentose carbohydrate, in a double-blinded, crossover study on markers of free radical production during hypoxic exercise. Seven healthy volunteers cycled at their lactate threshold for 25 minutes while inhaling 16% $O_2$ with a subsequent 60-minute resting period at room air. Subjects ingested either placebo or 7 g of ribose in 250mL of water before and after the exercise session. Urinary malondialdehyde (MDA) and plasma reduced glutathione levels increased significantly during placebo ingestion ($0.2;{pm};0.03;{mu}M/mg$ and $0.26;{pm};0.29;{mu}M$, respectively) but were lower with ribose supplementation ($0.04;{pm};0.03;{mu}M/mg$ and $0.38;{pm};0.29;{mu}M$, respectively; P < .05). Uric acid levels were similar between groups (ribose vs. placebo, $4.55;{pm};0.06;mg/dL$ vs. $4.67;{pm};0.06;mg/dL$). Ribose demonstrated a beneficial trend in lower MDA and reduced glutathione levels during hypoxic stress.