The present study investigated the effects of oxygen therapy upon human information processing for hypoxemic COPD patients. Each of ten patients was admitted to a general clinical research center for a two-day period. In a randomly counter-balanced factorial design, patients breathed either room air or enriched oxygen for either six hours or 20 minutes prior to testing. The tests evaluated speed of information processing, ability to detect correct sequence of tones, and serial memory. In addition, patients were evaluated on critical flicker fusion and story recall. The results suggested that acute oxygen therapy does not reverse information processing deficits observed in hypoxemic COPD patients.