Factors affecting cell viability, plating efficiency, and survival of hepatocytes after cryopreservation have been investigated. We focused especially on the effect of including trehalose and related oligosaccharides in the cryopreservation fluid. This was supplemented with either glucose, trehalose, maltotriose, or other sugars, in addition to dimethyl sulfoxide (10%) and first tested with primary rat hepatocytes cooled in a controlled rate freezer. After thawing, viability by trypan blue exclusion of cells frozen in oligosaccharide-supplemented medium was significantly higher than for those cryopreserved without oligosaccharides. Use of oligosaccharides with higher molecular weights resulted in greatest improvement in viability. Moreover, attachment and survival rates in plastic dishes were approximately 1.2-1.8-fold greater after freezing in the presence of di-, tri-, and tetrasaccharides. Human hepatocytes isolated from untransplantable liver showed the same tendency regarding viability, but cell adherence was not similarly improved by the addition of oligosaccharides. Possible reasons for these differences may be prior cell damage during extended cold ischemia of the human liver, donor age, or cell degradation caused by progression of fatty liver in humans, and/or species differences.