The sepsis syndrome represents a systemic response to infection and is defined as hypothermia (temperature less than 96 degrees F) or hyperthermia (greater than 101 degrees F), tachycardia (greater than 90 beat/min), tachypnea (greater than 20 breath/min), clinical evidence of an infection site and with at least one end-organ demonstrating inadequate perfusion or dysfunction expressed as poor or altered cerebral function, hypoxemia (PaO2 less than 75 torr), elevated plasma lactate, or oliguria (urine output less than 30 ml/h or 0.5 ml/kg body weight.h without corrective therapy). One hundred ninety-one patients with the sepsis syndrome were evaluated prospectively and comprised the placebo group of a multicenter trial of methylprednisolone in sepsis syndrome and septic shock. Forty-five percent of the patients were found to be bacteremic. Thirty-six percent of the patients were in septic shock (sepsis syndrome plus a systolic BP less than 90 mm Hg or a decrease from baseline in systolic BP greater than 40 mm Hg) on study entry. An additional 23% of the patients developed shock after admission with 70% doing so within 24 h of study entry. Shock reversal occurred with a 73% frequency. Twenty-five percent of the patients developed the adult respiratory distress syndrome (ARDS). Mortality for the patients with sepsis syndrome who did not develop shock was 13%. Mortality for the groups of patients with shock on admission and shock postadmission was 27.5% and 43.2%, respectively. Forty-seven percent of the bacteremic patients developed shock after study admission compared to 29.6% of the nonbacteremic patients (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)