UNLABELLED All the studies were performed on chronically cannulated, conscious Brattleboro rats, housed in metabolic cages under standard conditions. The renal excretory indices: diuresis (V), sodium (UNa.V), potassium (UK.V), chloride (UCl.V) and osmotic (Uosm.V) excretion were measured under the following experimental protocol: (1) controls, (2) 2% volume expansion (AVE)-0.9% NaCl i.v. for 2 min, (3) Dopamine (DA) receptor antagonist Flupentixol (FLU) 0.5 mg.kg-1 i.v., and (4) AVE 10 min after i.v. application of FLU. All the indices studied, given as cumulative curves, showed a firm linearity with time during the whole experimental period (5 h) in groups 1 and 2 (p < 0.05), while such a relationship was not found significantly in groups 3 and 4. AVE quickly, strongly and significantly (p < 0.01) increased V and especially UNa.V, UCl.V and Uosm.V. Pretreatment with FLU potently suppressed the effect of AVE on the renal excretion. FLU alone decreased almost equally V and saliuresis. IN CONCLUSION the DA antagonist FLU blocks the diuretic and saliuretic response to AVE probably by affecting tubular processes.