Acute and chronic cases of toxoplasmosis in Rattus norvegicus and Rattus rattus mindanensis caught in agricultural, commercial and residential sites in Dasmariñas, Cavite, Philippines were determined serologically. Fifty-eight percent of R. norvegicus and 42.0% of R. r. mindanensis were positive for anti-T. gondii antibodies (Abs). Infection was higher in male rats, and those caught in the commercial site had 100.0% seropositivity. Thirty percent of the R. norvegicus and 51.0% R. rattus mindanensis had acute infection, with 1:64-1:128 Abs titer. Seventy percent of the R. norvegicus and 49.0% of R. rattus mindanensis were chronically-infected with Abs titer 1:256-1:2048 and 1:256-1024, respectively. The association between the presence of infection with the rat gender and species and their collection sites was insignificant (p>0.05). In a related study, however, mice experimentally-inoculated brain tissue homogenate obtained from chronically-infected Rattus spp, manifested differences in the onset as well as, severity of infection which was histopathologically evaluated, suggestive of a possible difference in T. gondii parasite strain(s) infecting different rat populations.