The possible value of albumin in a rabbit model of the acid aspiration syndrome was studied. Hydrochloric acid was instilled into the respiratory tracts of three groups of rabbits: Group A received a high intravenous dose of human albumin (1.5 gm/kg body weight); Group B (control) was given Hartmann's solution, and Group C a low dose of albumin (0.25 gm/kg body weight). The total amount of intravenous fluids was identical in all groups. Serum and pulmonary edema fluid (PEF) concentrations of total protein were highest in Group A. Simultaneous concentration gradients between serum and PEF for total protein, human and rabbit albumin, and globulin fractions were not statistically different in the three groups. In Group A, PEF appeared first and PaO2, static compliance, and hematocrit decreased significantly more than those of the two other groups. Survival of animals in Group C was highest. An additional Group (D) of rabbits received the same high dose of albumin without acid aspiration. In Group D hematocrit decreased while serum total protein and pulmonary function remained unchanged.It seems that a high dose of albumin causes a further deterioration of lung function following acid aspiration because of extravasation into the interstitial space. The administration of low doses of albumin was not different than Hartmann's solution, but led to the best survival in our model.