ABSTRACT The effect of extractive haemodialysis and of postural changes on the plasma aldosterone concentration has been studied in 5 anephric children. The plasma aldosterone concentration tended to be lower after haemodialysis in spite of the extracellular volume depletion induced. No regular response occurred after orthostatism. There was no correlation between the plasma aldosterone and the plasma cortisol or the serum sodium concentration. A weak positive correlation was found between the plasma aldosterone and serum potassium concentration, suggesting that potassium may play a major role in aldosterone regulation in the anephric state.