Metacyclic trypomastigotes and epimastigotes of the Tulahuén strain of Trypanosoma cruzi were cultivated in a liquid metacyclic culture (LMC) medium. Trypanosome mixtures containing different percentages (7.5%, 15%, and 30%) of metacyclic stages obtained from these cultures were used to examine the effects of pH and anion exchange medium on the chromatographic isolation of the metacyclic stages. The isolations were performed on a DEAE-Sephacel, DEAE-cellulose DE 32, or DEAE-cellulose DE 52 columns at pH 4.0, 6.0, 8.0, or 10.0. All of the anion exchange media used exhibited the ability to enrich the metacyclic trypomastigote populations from trypanosome mixtures at all pH levels tested. However, the efficiencies varied: DEAE-cellulose DE 52 was about 15% less efficient than DEAE-Sephacel; DEAE-cellulose DE 32 was 10-20% less efficient than DEAE-cellulose DE 52. The greatest recovery of metacyclic stages was obtained by using DEAE-Sephacel at pH 8.0. This procedure was the most efficient for the isolation of metacyclic trypomastigotes from mixtures of stages of T. cruzi.