In the late 60s, A. Heidland and his collaborators were amongst the first to characterize the renal action of frusemide in preterminal renal failure by giving quantitative information on dose requirements, fractional Na and K excretion, effects on renal haemodynamics, and by recognizing reversible inner ear dysfunction as the major dose-limiting side-effects. These early studies have been largely reconfirmed. They have been extended by more clearly characterizing (a) altered pharmacokinetics of frusemide, e.g. the importance of altered transepithelial transport in the proximal tubule and intratubular protein binding, and (b) the mechanisms underlying altered pharmacodynamics, particularly high baseline fractional Na rejection and increased absolute distal Na reabsorption. Apart from increasing the dose of frusemide, continuous administration by infusion and combination of frusemide with thiazide diuretics have emerged as rational therapeutic strategies in chronic renal failure.