Thermodynamic solution theories are critical components in many of the mathematical models that are used to predict the behaviour of cells and tissues during cryopreservation. Although a number of solution theories have been proposed for use in cryobiology, most either do not account for the non-ideality of cryobiological solutions or require fitting to multi-solute data. However, there are at least two non-ideal solution theories available that can make predictions in multi-solute solutions while requiring fitting to only single-solute data in order to obtain all required thermodynamic coefficients: the Elliott et al. form of the multi-solute osmotic virial equation [J Phys Chem B 2007;111(7):1775–85] and the Kleinhans and Mazur freezing point summation model [Cryobiology 2007;54(2):212–222]. Herein, by way of comparison to available literature multi-solute osmometric data, we have evaluated the prediction accuracy of these two non-ideal solution theories in a variety of systems of interest to cryobiology. In doing so, we have also curve-fit a single, consistent set of literature single-solute osmometric data to obtain the required coefficients for each solution theory. Our results indicate that these two non-ideal solution theories provide similar performance overall, although each model has systems where it performs better. We have also found that both non-ideal models consistently provide more accurate predictions than an ideal dilute solution theory. The thermodynamic coefficients obtained in this work can be used with the multi-solute osmotic virial equation and/or the freezing point summation model to predict thermodynamic behaviour in a wide variety of multi-solute solutions. In addition, the results of our multi-solute solution analysis can be used to help in the selection of a non-ideal solution model when working with a particular combination of solutes. Funding sources: CIHR, NSERC, AITF, University of Alberta. J.A.W. Elliott holds a Canada Research Chair in Thermodynamics. This work has been submitted for publication to the journal Cryobiology.