Low-protein diets (<or=0.7 g/kg per day) have been advocated for over 70 years as a means of slowing the rate of progression of kidney disease and delaying the appearance of uraemic symptoms and need for dialysis. However, the available evidence to date suggests that the benefit : risk ratio of dietary protein restriction is not favourable in that: (i) compliance is generally sub-optimal; (ii) most of the published randomised controlled trials demonstrate that low-protein diets do not significantly slow the rate of kidney disease progression; (iii) meta-analyses of controlled trials have demonstrated strong evidence of publication bias favouring studies with positive, rather than negative, results; (iv) the optimal level and duration of dietary protein intake have not been defined; (v) there is no convincing clinical evidence that dietary protein restriction provides any benefit beyond that afforded by angiotensin blockade; and (vi) low-protein diets are associated with both statistically and clinically significant declines in nutritional markers in chronic kidney disease populations, which already have a high prevalence of malnutrition. Patients with progressive kidney disease are therefore likely to be better served by avoiding dietary protein restriction (thereby ensuring optimal preservation of their nutrition) and instituting alternative, proven renoprotective measures (e.g. renin-angiotensin system blockade, blood pressure reduction and statin therapy).