OBJECTIVE To study the effects of ketamine and alcohol on learning and memory in mice and its possible mechanism. METHODS Forty mice were divided into 4 groups: normal control group, ketamine group, alcohol group, and alcohol plus ketamine group. Ketamine and alcohol were given by intraperitoneal injection and intragastric administration, respectively, 1 time per day, for 14 days. The ability of learning and memory in mice was tested by the method of step-down and Morris water maze. Acetylcholine (ACh) and 5-hydroxy tryptamine(5-HT) in mice brain tissue were analyzed for the possible mechanism. RESULTS (1) Step-down: The treatment groups lessened the latency and added wrong times (P < 0.05). The number of errors in the combined treatment group significantly increased comparing with the single drug treatment group (P < 0.05). (2) Morris water-maze: The treatment groups prolonged the latency (P < 0.05), reduced the target quadrant activity time significantly (P < 0.05), and decreased the numbers of crossing the former platform significantly (P < 0.05). (3) Biochemical index determination: The concentrations of ACh and 5-HT in treatment groups decreased significantly (P < 0.05), showed a more decreasement comparing with the single drug treatment group. CONCLUSION Ketamine has a synergistic effect with alcohol on learning and memory impairment in mice, which may be related to the common inhibitive effect on the ACh and 5-HT.