The effects of chlorothiazide and furosemide on sodium and water excretion have been studied on anaesthetized dogs, previously subjected to unilateral splanchnicotomy. In all experiments ‘denervation diuresis’ was manifest in control periods with no significant differences in glomerular filtration rate. Intravenous chlorothiazide loading (5 mg/kg) and low dose of furosemide (0.5 mg/kg) resulted in a quantitative increase of denervation polyuria and natriuresis. Higher doses of furosemide (1.5–5.0 mg/kg) abolished denervation phenomenon. In postdiuretic periods increased sodium and water excretion from denervated kidneys could be observed, again. The results of chlorothiazide experiments and those obtained with the lowest dose of furosemide refer to a proximal tubular effect of splanchnicotomy. However, the disappearance of ‘denervation diuresis’ on more intense furosemide loading suggest that denervation may depress sodium reabsorption at more distal nephron segments, probably in the ascending limb of the loop of Henle. The role of intrarenal redistribution of blood flow and a possible shifting in filtration rate are discussed.