The purpose of this study is to clarify the effects of weaning methods to acquire the masticatory system on guinea pigs.

Forty guinea pigs were used. They were devided into four groups.

1)Control group: They were breeded with their dam in natural condition.

2)Pellet diet group: They were breeded with pellet diet and water alone from three days after birth.

3)Powdered diet group: They were breeded with powdered diet instead of hard food. 4)Synthetic milk group: They were breeded with milk. From 3 days after birth body weight, behavior and intraoral pressure were recorded.

Regarding body weight. There was no significant difference between four groups.

While findings showed no significant differences in the time to start the chewing-like movement between four groups, significant differeces in the time to stop the suckling-like movement and chewing rhythm formation time between the three non-control groups and the control group.

In conclusion it was suggested that the acquirement of the masticatory system on guinea pigs is affected by weaning method.