This study examined the impacts of intrauterine murine cytomegalovirus (MCMV) infection on the long-term learning and memory of offspring. Sexually matured male and female BALB/C mice without MCMV infection were identified by ELISA and then mated. Seventy pregnant mice were randomly divided into the virus group (n=40) and the control group (n=30), in which the pregnant mice were subjected to placenta inoculation of MCMV suspension (1 mu L, 1x10(6) PFU) or the same amount of cell culture medium, respectively, at gestational age of 12.5 days. Some pregnant mice [virus group (n=20), control group (n=15)] were sacrificed by cervical dislocation at gestational age of 18.5 days, and the head circumference and brain weight of the mouse fetuses were measured, and the MCMV infection in their brain tissues was detected by PCR. The other pregnant mice [virus group (n=20), control group (n=15)] delivered naturally, and the learning and memory capability of the offspring at 70-day-old was analyzed by Morris water maze test. The results showed that 28.57% mouse fetuses in the virus group developed viral infection in the brain. Their head circumference and brain weight were significantly reduced as compared with those in the control group (P<0.01). The Morris water maze test revealed that the mouse offspring in the control group found the platform with straight-line trajectories after training. In contrast, the counterparts in the virus group intended to enter the central area, but looked for the platform with a circular trajectory. And the infected mice exhibited prolonged swimming distance and swimming latency (P<0.01). It was concluded that: (1) placenta inoculation of MCMV can cause fetal brain infection and intrauterine development retardation; (2) the offspring of MCMV placenta inoculation mice showed a long-term decline in learning and memory capability.