During differentiation of the dividing epimastigote to the non-dividing metacyclic trypomastigote form of the parasitic protozoan Trypanosoma cruzi there is a marked reduction in the rate of synthesis of the major proteins alpha- and beta-tubulin. Our results indicate that the control of synthesis of these proteins during the differentiation event is exerted at the level of alpha- and beta-tubulin mRNA accumulation.