This Study was carried out ot investigate the effects of concentration and equilibration time of cryoprotective aagents on survival rate of slowly and ultrarapidly frozen porcine embryos. The porcine embryos following dehydration by cryoprotective agents and 0.25M sucrose were slowly freezed(from 2$0^{circ}C$ to -7$^{circ}C$/-1$^{circ}C$/min., from -7$^{circ}C$ to -35$^{circ}C$/-0.2$^{circ}C$/min., from -35$^{circ}C$ to -38$^{circ}C$/-0.3$^{circ}C$/min.) by Cell Freezer and directly plunged into liquid nitrogen and thawed in 38$^{circ}C$ water bath. Survival rate was defined as development rate to the morula and blastocyst stage after in vitro culture or by FDA test. The results are summarized as follows : 1. The survival rates of porcine embryos after slow frozen-thawing in the freezing medium of 0.25M sucrose added 2.0M glycerol, 3.0M DMSO, 2.0M propanediol or 2.0M glycerol＋2.0M propanediol was 80.6, 84.7, 75.0 or 78.8%, respectively. 2. The survival rates of porcine embryos after slow frozen-thawing in the freezing medium of 0.50M sucrose added 2.0M glycerol, 3.0M DMSO, 2.0M propanediol or 2.0M glycerol＋2.0M propanediol was 80.9, 82.4, 73.1 or 77.1%, respectively. 3. The survival rates of porcine embryos after ultrarapid frozen-thawing in the freezing medium of 0.25M sucroese added 2.0M glycerol, 3.0M DMSO, 2.0M propanediol or 2.0M glycerol＋2.0M propanediol was 65.3, 68.6, 63.2 or 59.9%, respectively. 4. The survival rates of porcine embryos after ultrapid frozen-thawing in the freezing medium of 0.50M sucrose added 2.0M glycerol, 3.0M DMSO, 2.0 propanediol or 2.0M glycerol＋2.0M propanediol was 67.5, 62.9, 56.9, or 62.8%, respectively. 5. The higher survival rate of porcine embryos was attained at the short period ofequilibration time(5min.) in the freezing medium added 0.25M sucrose and 3.0 DMSO compared to those of 10 or 20min. equilibration time in the same condition.