Trypanosoma cruzi, the parasitic protozoan that causes Chagas disease, contains a major cysteine proteinase, cruzipain. This lysosomal enzyme bears an unusual C-terminal extension that contains a number of post-translational modifications, and most antibodies in natural and experimen-tal infections are directed against it. In this report we took advantage of UV-MALDI-TOF mass spectrometry in conjunction with peptide N-gly-cosidase F deglycosylation and high performance anion exchange chroma-tography analysis to address the structure of the N-linked oligosaccharides present in this domain. .