Estradiol benzoate (E2B) was intramuscularly injected in 3 groups of weaned sows at a dose of 0.2 mg/head on day 0 and on day 2 and at a dose of 0.4 mg/head on day 2, respectively. The blood concentration of LH rose to a peak 60-66 hr after E2B injection. The rates of the occurrence of estrus after E2B treatment in these groups were 85.7, 89.5 and 87.5%, respectively, with no significant differences compared to the control except for the second group. The farrowing rates in the 3 treated groups were 100, 86.8 and 61.9%, respectively, and the value in the third group was significantly lower compared to the control (p < 0.05). There were no significant differences in average litter size between the control and any of the treated groups.