Loop diuretics are powerful drugs able to increase urinary sodium and water excretion even in conditions of marked impairment of renal function. Loop diuretics are useful in preventing or ameliorating the course of acute renal failure. This effect may be obtained when they are used within 18 h after the ischaemic and/or toxic event. Loop diuretics reduce tubular work, providing resistance to cellular ischaemia. Other important beneficial effects include tubular wash-out of cellular debris and inhibition of tubuloglomerular feedback. Among vasodilators, dopamine, when used at 'dopaminergic dosage' is useful in preventing acute renal failure. Its efficacy is demonstrated in several situations of renal hypoperfusion, i.e. salt depletion, cyclosporin administration, and therapy with recombinant interleukin 2 in cancer patients. According to our studies it appears that dopamine should be used in the early phases of acute renal failure to improve renal perfusion, re-establish glomerular filtration rate, and increase tubular flow.