Abstract: The activities of L−alanine amino transferase and L−aspartate amino transferase in rabbit serum were assayed in the presence and absence of graded doses of congo red administered i.p. Blood was collected for a period of seven days from three groups of rabbits administered with 45 mg kg-1 body wt., 67.5 mg kg-1 body wt body and 90.0 mg kg 1 body wt., respectively and used for enzyme analysis. The result obtained showed that the two enzyme activities were inhibited significantly (P< 0.05) and the degree of inhibitions were dose-dependent with respect to the control group. Dose dependent inhibition of Congo red on the two transanminases was substantiated by varying percentage decreases of the enzyme activities as 37, 58.7 and 60.2% for the groups 1, 2 and 3, respectively for aspartate amino transferase. The same pattern of inhibition was observed for alanine amino transferase suggesting that both enzymes may be inhibited by similar mechanism.