This paper compiles recent data on the theoretical prediction of the water activity (aw) of selected saturated salt solutions, unsaturated NaCl and LiCl solutions, and H2SO4 solutions. These results are presented in tabular form in such a way that they can be safely used as reference sources for aw determination in the range of microbial growth (i.e. about 0.57-0.97) and at different temperatures.