This study was conducted to investigate the effects of fetal bovine serum(FBS), calf serum(CS) and human serum(HS) on in vitro maturation of porcine follicular oocytes. The results obtained were summarized as follows : 1. The maturation rates of oocytes cultured in medium containing FBS 5, 10, 20 and 30% were 47.0, 63.5, 48.4 and 43.2%, respectively. There were significantly higher than those of non-treated group(25.3%). And the highest maturation rate was the 10% treatment. 2. The maturation rates of oocytes cultured in medium containing CS 5, 10, 20 and 30% were 55.2, 56.6, 59.4 and 46.5%, respectively. There were significantly higher than those of non-treated group(25.3%). And the highest maturation rate was the 20% treatment. 3. The maturation rates of oocytes cultured in medium containing HS 5, 10, 20 and 30% were 74.5, 78.2, 73.1 and 68.6%, respectively. There were significantly higher than those of non-treated group(29.6%). And the highest maturation rate was the 10% treatment.