Ketamine, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, produces behavioral changes and cognitive deficits related to schizophrenia symptoms. The objective of the research was to investigate the effects of ketamine on learning and memory function of mice by Morris water maze test. Materials and methods: 105 male healthy mice, aged 7-8 weeks were randomly divided into 6 ketamine groups: Ket 10 (10 mg/kg), Ket 15 (15 mg/kg), Ket 20 (20 mg/kg), Ket 25 (25mg/kg), Ket 30 (30 mg/kg), Ket 35 (35 mg/kg) and control group. The results showed that the latency to find platform in Ket 15, 20, 30 and Ket 35 groups was significantly longer than that of control group (p 0.05). Distance travelled in Moris water maze of mice in Ket 10, 15,20,25 and 30 groups was significantly higher than that of control group (p 0.05). There was no difference in average velocity within 7 groups (p 0.05).