Solute-free water clearance increased by 186% in water loaded rats treated with glucagon-like peptide 1 compared to untreated group. The effect of glucagon-like peptide 1 was reproduced in experiments with its synthetic analogue exenatide. Serum osmolality in water loaded rats treated with exenatide was closer to normal level on 30, 45, 60 min of experiment compared to the untreated group and reached the control value in 60 min. Administration of glucagon-like peptide 1 receptor antagonist to water loaded rats delayed (5 ml per 100 g bw) or prevented (2 ml per 100 g bw) increase in solute-free water clearance. The obtained data suggest the involvement of glucagon-like peptide 1 in osmotic homeostasis and indicate the unique physiologic role of incretins in regulation of water balance.