Charales populations from calcareous tropical streams in central Mexico were investigated through the sampling of six stream segments during the dry season, the most favourable growth period. Five taxa were found: Chara haitensis, C. vulgaris var. nitelloides, C. zeylanica var. diaphana, Nitella furcata var. sieberi and N. tenuissima var. tenuissima. Chara haitensis and N. tenuissima are reported for the second time in central streams and described in detail for the first time in the freshwater green algal flora from Mexico. Physical and chemical water quality data were also recorded in the investigated environments. All taxa were found at high temperatures (22-28 ºC), neutral to moderately alkaline waters (pH 7-8) with high ionic content (total dissolved solids 593-1884 mg l-1, specific conductance 826-1952 µS cm-1), with sulfate-bicarbonate/calcium as dominant ions. The populations were associated with slow current velocity (≤ 30 cm s-1), shallow water depth (≤ 41 cm) and silt to sand substratum with high organic matter content. The taxa were found in a wide range of incident radiation (340-2234 mol photons m-2 s-1), except for N. furcata var. sieberi which was found in shady sites (24 mol photons m-2 s-1). All the populations investigated were found in mesotrophic to eutrophic conditions.