The response of Day Eight equine embryos to saccharide solutions was investigated as a first step in their potential use as non-permeating cryoprotective agents. Embryos were exposured to seven increasing concentrations of either sucrose or galactose at a temperature of 22°, 30° or 37°C. Each embryo was then rehydrated by exposing it to the same solutions in reverse. Embryos underwent osmotic dehydration, independent of treatment group, but embryo size had a significant effect on the response pattern. Embryos < 500µm dehydrated osmotically to 20% of their original volume. Those > 500µm exhibited a delayed response and only dehydrated to 40% of their original volume. When placed into decreasing concentrations, embryos partially rehydrated. Pre- and post-treatment embryo quality was compared and embryos were stained to determine the amount of apoptosis, with no difference in embryo survival between treatments. Results indicate that saccharides show promise for use in equine embryos < 500µm. / Ontario Veterinary College, Equine Guelph, Partnar Animal Health