Alterations in rat renal glucose transport following in vivo use of Freund's adjuvant were examined. Lewis-Brown Norway rats were placed in four separate injection groups: 1) tubular basement membrane plus adjuvant [complete Freund's adjuvant (CFA) plus pertussis]; 2) adjuvant (CFA plus pertussis); 3) CFA only; or 4) pertussis only. Renal handling of glucose was assessed 14 days after a single injection. No in vivo changes were noted. No histologic differences among groups were noted. However, brush border membrane vesicles prepared from animals in groups 1, 2, and 3 showed a marked decrease in glucose uptake. Further, Michaelis-Menten kinetics demonstrated a decrease in apparent Km and Vmax for glucose in groups 1, 2, and 3. CFA alone can cause a change in brush border membrane vesicle uptake of glucose. The pathogenic mechanism behind CFA-induced transport changes remains unclear. However, studies employing CFA cannot dismiss Freund's adjuvant as "inert" and must take into account functional changes created by CFA alone.