This study was conducted to investigate the effect of $\beta$-mercaptoethanol ($\beta$-ME) and cysteamine on in vitro maturation of porcine follicular oocytes. The results obtained were summarized as follows : 1. When the immature oocytes were cultured at 0, 10, 50, 100 and 200 $\mu$M of $\beta$-ME for 36h, the GVBD rates were 91.6, 92.5, 91.8, 91.9 and 92.7%, respectively, and the maturation rates of the oocytes with metaphase-II were 49.6, 41.7, 32.5, 34.1 and 35.4%, respectively. Thus, lower maturation rate was shown in $\beta$-ME treated groups of 50, 100 and 200 $\mu$M as compared to control (non-treated) group (P＜0.05). After 44h of culture in the same treatments of $\beta$-ME, the GVBD rates of porcine oocytes were 91.8, 90.4, 92.5, 91.2 and 93.9%, respectively, and the maturation rates were 71.9, 58.8, 56.7, 62.2 and 56.5% respectively. All treated groups of $\beta$-ME showed lower maturation rates than the control group (P＜0.05) 2. When the immature oocytes were cultured at 0, 10, 50, 100 and 200 $\mu$M of cysteamine for 36h, the GVBD rates were 90.6, 86.3, 88.2, 87.2 and 90.0%, respectively, and the maturation rates were 53.8, 45.1, 54.4, 57.5 and 63.3% respectively. Especially, the maturation rate of 200 $\mu$M treated group was significantly higher than those of control group (P＜0.05). After 44h of culture in the same treatments of cysteamine, the GVBD rates of porcine immature oocytes were 89.5, 93.1, 85.1, 89.8 and 91.3%, respectively, and the maturation rates of the oocytes with metaphase- II were 84.2, 77.6, 66.0, 67.8 and 78.3%, respectively. Especially, the maturation rates of 50 and 100 $\mu$M treated groups were significantly lower than those of control group (P＜0.05).