A reduction in body water equivalent to a body mass loss of 2% has been shown to impair exercise performance[1]. The effectiveness of rehydration solutions is of importance when subsequent exercise sessions are planned. Addition of sodium[2], carbohydrate[3] and protein[4] to rehydration solutions has been shown to enhance drink retention, but these studies have typically not provided food in the post-exercise period. Food would usually be consumed post-exercise but it is unknown how this will influence the efficacy of rehydration solutions. This study investigated the rehydration effects of a 50 mmol/L NaCl solution or water when consumed alongside a post-exercise meal.Eight healthy participants (5 male, 3 female) aged 20-25 y were dehydrated by (mean ± SD) 1.48 ± 0.44% of body mass by intermittent cycling in the heat (33.3 ± 1.7°C, 52 ± 13% relative humidity). Post-exercise, participants consumed a volume of drink equivalent to 150% body mass loss of a 50 mmol/L NaCl solution or water together with a standardised meal equivalent to 30% estimated daily energy expenditure. The drink volume was provided in four equal boluses over sixty minutes, whilst the meal was consumed with the second, third and fourth boluses. Urine volume and osmolality was measured before exercise, post-exercise and 0, 1, 2 and 3 hours post-rehydration. Data was analysed using t-tests and ANOVAs where appropriate.No significant differences between trials were found for percentage body mass lost (P= 0.793), sweat loss (P= 0.988) or drink volume (P = 0.995). Cumulative urine volume during the recovery period was higher (P= 0.035) in the water trial (981 ± 458 mL) than in the NaCl trial (577 ± 345 mL). A greater percentage of drink was retained (P= 0.013) during the NaCl trial (60 ± 29%) than during the water trial (33 ± 28%). Participants were in negative net fluid balance after exercise and positive fluid balance following rehydration (P < 0.05). No differences (P > 0.05) from pre-exercise net fluid balance were observed during the recovery period on either trial however participants tended to be in negative fluid balance (P = 0.072) 3 hours after rehydration on the water trial. Previous studies have suggested that the addition of sodium to rehydration solutions results in a reduction in urine output and a beneficial effect on rehydration after exercise-induced dehydration by attenuating the decline in plasma osmolality and arginine vasopressin secretion after drink ingestion[2]. The results of this study suggest that the addition of sodium to a rehydration solution when consumed alongside food still results in differences in urine output and fluid retention when compared with water. It is interesting to note that participants were considered to be euhydrated throughout the recovery period when water was ingested alongside food.