The DNA contents of three different Trypanosoma cruzi strains were compared by direct microfluorometry. The maximal difference found was 40% of the lowest value. Two of the cloned strains, reported in an earlier study to differ by 48% in their total DNA content, showed a difference of 33%. The kinetoplast of the Y strain made up about one third of its total genome. The absolute DNA content of T. cruzi was estimated at 125 to 200 fg.