It is now well established that the antidiuretic response to vasopressin is modulated by changes in aquaporin-2 (AQP2) expression in response to hydration status. While vasopressin itself is one signal driving expression, other signals also play a part. In this study, we planned to investigate whether prostaglandins, known to modulate AQP2 trafficking, may play a role in this process. Male Wistar rats were kept in metabolic cages, with either free access to water and food, or were given 15 g of food gelled with water, such that they were fluid restricted or fluid loaded. The effects of oral administration of two structurally different NSAIDs, indomethacin and ibuprofen, and a COX-2-selective NSAID, meloxicam, on urine output and AQP2 expression were investigated in kidneys removed under terminal anesthesia. All the NSAIDs decreased AQP2 expression significantly in water-restricted rats but did not significantly alter PGE excretion. In water-loaded rats, the effects were less marked, and meloxicam had no significant effect. Consistent with this, ibuprofen prevented the increase in AQP2 expression seen in response to dehydration. These results demonstrate that NSAIDs decrease AQP2 protein abundance, particularly during adaptation during dehydration. This may be of particular significance in older and critically ill patients, who are prone to dehydration.