Thirty-one compounds have been identified that act as cryoprotective agents for cultured mammalian cells. Eight compounds were comparable to dimethylsulfoxide (DMSO) in cryoprotective effectiveness. Many of the cryoprotective compounds studied also (a) promote cell fusion and (b) induce cell differentiation in erythroleukemia and other cell systems. Thus, previously unrecognized effects on the differentiated state of cells may occur when cells are treated with cryoprotective agents.