Two-cell preimplantation mouse embryos were exposed in vitro to lidocaine (0 to 1, 000 μg/mL) for 72 h to determine the effects of this anesthetic on subsequent cleavage and development during prolonged exposures. Embryonic development was monitored each 24 h for 3 d. Lidocaine adversely affected the in vitro development of the mouse embryos, altering the distribution of the development stages at the evaluated culture times. The percentage of two-cell embryos that cleaved and developed to more advanced stages was decreased by the exposure to lidocaine. After 24 h of culture, two-cell embryos were arrested before completion of cellular division; this occurred in 30% of the embryos at concentrations of 10 to 100 μg/mL and in 73.2% of the embryos with 1, 000 μg/mL. After 48 h the blastomeres of the arrested embryos began to degenerate, showing lysis or fragmentation. At the lowest concentration, 14.9% of the arrested embryos exhibited the capacity to recover. These embryos continued their cleavage and normal development towards blastocyst formation. The cytotoxic effect and arrest at the two- cell stage were observed in a dose-dependent manner after 72 h of culture. We conclude that sensitivity to lidocaine embryotoxicity occurs during a window at the two-cell stage.