Woodrow AD, Webb JT, Wier GS. Recollection of hypoxia symptons between training events. Aviat Space Environ Med 2011; 82:1143–7. Introduction: The well-established technique of mask-off hypoxia training in a hypobaric training environment elicits symptoms that are correlated with in-flight symptoms reported by aircrew. Aircrew receive training on recognition of symptoms and response early in their flying career and accomplish refresher training on a 5-yr cycle. The symptoms reported after acute hypoxia represent cognitive and psychomotor impairment. The purpose of this study was to evaluate the correlation of symptoms experienced during hypoxia training and recall of symptoms from the training sessions 5 yr previously. Methods: A survey listing 18 symptoms of hypoxia and severity of condition was presented to 1123 aircrew attending refresher training at 10 U.S. Air Force Aerospace Physiology Training Units prior to and immediately following hypoxia training in the hypobaric chamber. Results: The five symptoms most commonly reported following hypoxia training are: lightheaded/dizzy, dizziness, mental confusion, visual impairment, and tingling. The hypoxia symptom “lightheaded/dizzy” recorded the highest frequency of all 18 symptoms. Lightheaded/dizzy frequencies for both previous and current hypoxia training were 67.2% and 72.3%, respectively. This symptom remained consistent throughout all data analysis, retaining the highest frequency in all levels of severity (mild, moderate, and extreme) for both the previous hypoxia training and current hypoxia training. Discussion: The similarity of symptoms recalled between hypoxia training events provides strong evidence that hypoxia training is an effective method of establishing recognized decrements that may influence performance in flight.