Summary Male Sprague-Dawley rats were subjected to full thickness burns of 26%, 20% and 14% body surface, respectively. A reduction in burned area was correlated with (a) increased survival, (b) decreased incidence of positive Combs' tests and (c) a lengthening in the postburn time at which the Combs' tests could be detected. Hemato-crits, reticulocyte numbers and serum protein values showed only partial correlation with the percent of area burned. Postburn splenomegaly was greater in positive survivors than in those that were negative. Blood samples cultured on blood agar plates showed a low incidence of bacteremia in the A and B groups; all C group animals were negative.