Over a 2.5 year period, the fluid management of 600 hypotensive patients entering our surgical emergency department was evaluated during a prospective clinical trial of a resuscitation algorithm. The major clinical determinants (low mean arterial pressure, age, severity of illness, primary illness or injury, amount of blood loss, volume of fluids given, use of a protocol or clinical algorithm and satisfactory compliance with the algorithm) were controlled by grouping the patients into specific strata; the resuscitation times were almost always shorter with a regimen of about one-fourth colloids than with crystalloids only. This is consistent with the observations of greater increases in hemodynamic and oxygen transport variables after albumin than after lactated Ringer's solution when the latter was given in either 2 or 4 times the volume.