Acute neuropsychological changes due to high altitude climbing without supplementary oxygen are well known. However, many climbers report vague symptoms of brain dysfunction after return to sea level suggesting that long-lasting neuropsychological impairment may ensue even after a single ascent. In this study we evaluated a series of neuropsychological functions in a group of 11 climbers who ascended over 5000 m. Besides memory, also reaction time and concentration were less efficient when the climbers were evaluated 75 days after their return to sea level, confirming that even a single high altitude climb may be harmful for central nervous system functions.