Twenty-three women of ages 13 to 44 years were hospitalized with illnesses fulfilling the criteria of the case definition for the toxic-shock syndrome (TSS) associated with coagulase-positive staphylococci. Disease onset occurred during menses in 22, and all were oliguric when admitted. Prolonged hypotension and a reduced central venous pressure were common features. Measurements of urine volume and creatinine clearance in eight patients identified two types of acute renal failure, oliguric and nonoliguric, and prerenal azotemia related to intravascular volume depletion. Urinary sodium excretion and measurement of the renal index (UNa divided by U/PCr) provided further support for the presence of both prerenal and intrinsic renal failure. Hemodialysis was required in one patient in whom findings on renal nuclide scan were consistent with acute tubular necrosis. Pyuria was frequent, but proteinuria and more than five erythrocytes per high-power field were infrequent. Other features included initial hyponatremia and the combination of hypoproteinemia, hypoalbuminemia, hypocalcemia and hypophosphatemia of several days' duration. The hypoalbuminemia was believed to be due to exudation of protein from the intra- to the extravascular space. The hypoalbuminemia was believed to be due to exudation of protein from the intra- to the extravascular space. The hypocalcemia was probably related to the hypoalbuminemia. The pathogenesis of hypophosphatemia in the presence of acute renal failure is unclear. Following the intravenous administration of colloids, fluids and, in seven patients, dopamine, all recovered from the acute illness.