The prevalence of antibodies against Seoul virus was investigated in 655 wild rats (Rattus norvegicus, R. rattus, R. rattus diardii, R. exulans, R. tiomanicus) captured in seven port areas of Indonesia. Twenty-four of 238 R. norvegicus, one of 142 R. rattus and one of 102 R. exulans from two port areas had the antibodies against Seoul virus.