The worldwide prevalence of obesity and its associated metabolic and cardiovascular disorders has risen dramatically within the past 2 decades. Our objective is to review the mechanisms that link obesity with altered kidney function. Current evidence suggests that excess weight gain may be responsible for 65-75% of the risk for arterial hypertension. Impaired renal pressure natriuresis, initially due to increased renal tubular sodium reabsorption, is a key factor linking obesity with hypertension. Obesity increases renal sodium reabsorption by activating the renin-angiotensin and sympathetic nervous systems, and by altering intrarenal physical forces. Adipose tissue functions as an endocrine organ, secreting hormones/cytokines (e.g., leptin) which may trigger sodium retention and hypertension. Additionally, excess visceral adipose tissue may physically compress the kidneys, increasing intrarenal pressures and tubular reabsorption. Eventually, sustained obesity via hyperinsulinemia, due to resistance to insulin, causes hyperfiltration, resulting in structural changes in the kidneys--glomerular hyperthrophy and occasionally focal segmental glomerulosclerosis. The consequences of kidney injury are continuous loss of glomerular filtration rate, further increase of arterial pressure and escalation of cardiovascular morbidity and mortality. There is a growing awareness of the renal consequences of obesity, and considerable progress is being made in understanding its pathophysiology. Weight reduction results in lowered proteinuria. Aside from low sodium diet and exercises, more widespread use of renoprotective therapy (e.g., ACE inhibitors and statins) in treatment of hypertension in obese subjects should be advocated. Renal protection should result in reducing the cardiovascular complications of obesity.