Fourteen adult patients (mean age, 35 yrs) with 20-60% total body surface area (TBSA) burns (mean, 35%) were resuscitated using hypertonic sodium lactate (HSL: sodium = 250 mEq/L). Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), angiotensin II (A-II), epinephrine (E) and norepinephrine (NE) were measured on admission and for 7 days following burn injury. Serum sodium concentrations and osmolalities were lowest on admission, and were persistently elevated following HSL resuscitation. Plasma AVP levels were highest on admission and correlated with the size of the burn injury. Between days 4 and 5 plasma ANP levels rose while plasma AVP levels returned to normal. Plasma concentrations of AVP and ANP did not correlate with serum osmolality or serum sodium concentrations on admission or after HSL resuscitation. Plasma levels of A-II, NE and E were elevated throughout the 7-day period and were unrelated to the size of the burn.