This review outlines: a) the main biochemical and biological properties of the complement system (C) components; b) the manner through which they interact in the two distinct routes of C activation, the classical and the alternative pathways, to generate the enzymes C3 and C5 convertases responsible for release of the peptides C4a, C3a and C5a endowed with the properties of mediating the early events of the inflammatory process or the potentially cytolytic complex C5b-C9; c) the main features of control of these activation processes; d) the identification of cell surface components present in the trypomastigote forms of Trypanosoma cruzi possibly involved in the mechanisms developed by this parasite to evade C lysis; e) the inactivation or removal of these cell surface components by enzymatic (trypsin or papain), chemical (periodate) or physical (heating at 45 degrees C) treatments; f) isolation of these components by chromatographic methods; and, g) demonstration that some of these cell surface components interfere with C3 convertase formation or action in a manner similar to the decay accelerating factor (DAF).