Eggs of Toxocara vitulorum were harvested from the feces of infected buffalo calves and embryonated in vitro. Optimum conditions for hatch and culture of the second-stage larvae were determined. Maximum hatch of larvae occurred from eggs that were decoated by treatment with saturated Ca(OCl)2 for 16-24 min followed by treatment with CO2 and incubation at 37 C. Larvae could be cultured in RPMI-1640 medium for up to 3 mo but survived for only 3 wk in Eagle's minimum essential medium.