Both Damietta and Qualyobia governorates were examined for the seasonal activities of Rattus species and subspecies and their natural infection with Trypanosoma lewisi. The common domestic rodents identified were Rattus r. alexandrinus, R. r. frugivorus and Rattus norvegicus. They were common all the year round except in winter for R. norvegicus in Damietta. Gravid females of the three rodent species, were identified in Damietta in summer, in addition to Autumn for R. norvegicus only. In Qualyobia, gravid females of the three rodent species, were identified in spring, in addition to autumn for R. norvegicus only. The heaviest rodent in weight, was R. norvegicus, in summer (Damietta), and in spring (Qualyobia). The three rodent species were naturally infected with T. lewisi. The whole results were discussed on the light of the work done before, with reference to the feasible time to apply rodenticides.