Objectives Water is an essential nutrient for thermoregulation, metabolism, cognition, and overall physiological homeostatic function. However, aging adults display a blunted thirst mechanism and subsequently have an increased risk for dehydration or hyponatremia. Fluid consumption behaviors are modifiable and the importance of practicing adequate drinking behaviors for aging adults is amplified during exercise. Identification of aging adult’s hydration beliefs and how they attain hydration advice could provide valuable information into ways to promote better drinking habits to reduce fluid imbalances. Thus, this investigation evaluated the knowledge, beliefs and behaviors of middle-aged cyclists (MA) that were associated with hydration status and drinking behavior, before and during a 164-km mass-participation event (ambient temperature, 33.3±2.8ºC(mean±SD)). Design: This cross-sectional field study retrospectively grouped participants by their second urine specific gravity (U sg ) measurement of the event morning prior to a mass participation cycling event. U sg was assessed via handheld refractometer. Setting The Hotter N’ Hell Hundred 164-km cycling event in Wichita Falls, Texas during the month of August. Participants 36 male recreational cyclists (age, 53±9 y(mean±SD)). Measurements Participants were grouped according their urine specific gravity as either slightly hyperhydrated (SH; n=12, U sg ≤1.014), euhydrated (EUH; n=12, U sg , 1.015-1.020), or slightly dehydrated (SD; n=12, U sg ≥1.021). Exercise histories and questionnaires were recorded 24-48 h prior to the cycling event. Results Regardless of pre-event hydration status, all groups experienced a similar body mass loss during the 164-km event and finished with statistically similar exercise times; also, drinking behavior within all groups was influenced by multiple factors. The primary factors associated with MA cyclist drinking behavior were trial and error/personal history and thirst; further, the majority of cyclists (≥65%) in SH, EUH, and SD believed that dehydration affects performance negatively. The least important factors included rehydration recommendations from scientific and sports medicine organizations, plus information from sports drink manufacturers. Conclusion Considering the complexity of the present findings and the physiological changes that accompany aging such as delayed thirst perception, we recommend that MA cyclists formulate an individualized drinking plan that is based on observations during exercise.