Objectives: The aim of this study was to assess toxicities of cryoprotectants. Methods: Toxicities of two cryoprotectants, dimethyl sulfoxide (DMSO) and 1, 2-propanediol (PROH), were investigated using a murine embryo model. Female F-1 mice were stimulated with gonadotropin, induced ovulation with hCG and mated. Two cell embryos were collected and cultured after exposure to either DMSO or PROH. Embryo development was evaluated up to the blastocyst stage. Blastocysts were stained with bis-benzimide to evaluate the cell count and with terminal deoxynucleotidyl transferase mediated dUTP nick labeling (TUNEL) to assess apoptosis. Results: The total cell count of blastocysts that were treated with DMSO at the 2-cell stage was significantly lower than that were treated with PROH ($75.9{pm}27.0$) or the control ($99.0{pm}18.3$) (p<0.001). On comparison of two cryoprotectant treated groups, the DMSO treated group showed a decreased cell count compared with the PROH treated group (p<0.05). Both DMSO ($14.2{pm}1.5$) and PROH ($11.2{pm}1.4$) treated groups showed higher apoptosis rates of cells in the blastocyst compared with the control ($6.2{pm}0.9$, p<0.0001). In addition, the DMSO treated group showed more apoptotic cells than the PROH treated group (p<0.001). Conclusions: The potential toxicity of cryoprotectants was uncovered by prolonged exposure of murine embryos to either DMSO or PROH at room temperature. When comparing two cryoprotective agents, PROH appeared to be less toxic than DMSO at least in a murine embryo model.