Trypanosoma cruzi survives in vertebrate and invertebrate hosts and has developed mechanisms that allow it to adapt to changes in the microenvironment such as temperature, pH, and ionic composition. Most of its calcium is concentrated in an organelle named the acidocalcisome, which is acidified by a (V-H+)-adenosine triphosphatase and has H+/Ca2+ counter-transportation for calcium uptake. In this work, acidocalcisomes were examined using different transmission electron microscopy techniques. In thin sections of different stages, acidocalcisomes presented a circular shape with an electron-dense inclusion containing P3-, Ca2+, Na+, Mg2+, K+, and Zn2+. They could be distinguished from gold-labeled albumin-containing reservosomes in whole epimastigotes, and a morphometric analysis showed higher amounts of these organelles in amastigotes as compared with epimastigotes and trypomastigotes. It is possible that this variation in the amount of acidocalcisomes in the different evolutive stages could reflect adaptation mechanisms used by the parasite to survive and multiply in different environmental conditions.