Abstract Oocytes were aspirated from caprine ovaries, washed and cultured in TCM-199 containing penicillin, streptomycin and 10, 15, or 20% of fetal bovine serum (FBS), estrous sheep serum (ESS) or estrous goat serum (EGS). After 24–26 h culture, oocytes were separated from cumulus and corona cells by hyaluronidase and by passing through a fine pipette, fixed in acetic alcohol, stained with aceto orcein and observed under a phase-contrast microscope for evidence of maturation. High maturation rates (74–94%) were observed in all concentrations of the three different sera examined. No significant difference was observed between different concentrations and among different sera. Almost no maturation (4%) was observed in the medium lacking protein supplement. In conclusion, these sera with the concentrations examined can be substituted for one another for in vitro maturation of caprine oocytes.