This study was conducted to investigate the effects of active immunization against cholecystokinin 8 (CCK(8)) on the content of serum CCK, expression of CCK, and CCK receptor gene in pigs. The subjects for this experiment were 15 pigs divided into three groups (5 pigs per group). The treated groups were immunized with CCK(8) conjugated to human serum albumin (HSA). The control group was immunized with same dosage of HSA. The average daily gain of pig fed with 250 microg CCK was significantly increased (P < 0.05), compared with the control group (0 microg CCK). The content of CCK(8), insulin, and leptin in serum was significantly (P < 0.05) decreased and the titer of CCK(8) antibody was significantly (P < 0.05) increased in treated groups compared to the control group. The levels of CCK gene and CCK receptor gene expression in jejunum, pituitary, and pancreas of the treated groups were significantly (P < 0.05) lower than that of the control group. It is concluded that optimal active immunization against CCK(8) could increase the content of CCK antibody and suppress CCK gene and CCK receptor gene expressions and in result improve feed intake and growth performance of pigs.