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Stability constants and dissociation rates of alkali metal cryptates have been measured in propylene carbonate, and the corresponding formation rates obtained from a combination of the two. Qualitatively, the variation in stability constants with cation size and ligand is similar to that in water, but the complexes are up to 107 times more stable in propylene carbonate. It is shown that for a given ligand the free energy transfer of the cryptates from water to propylene carbonate varies systematically with the cation enclosed and tends to be at a minimum for the most stable cryptate. The higher stability constants in propylene carbonate relative to water are a result of both smaller dissociation rates and, to a lesser extent, larger formation rates. Within propylene carbonate, the cryptand selectivity is reflected almost entirely in the dissociation rates. The dissociation rates are much more susceptible to acid catalysis in propylene carbonate than in water.