Recent studies indicate that domestic rats (Rattus norvegicus) from harborside areas within port cities of the United States are infected with a Hantaan-like virus. The geographical distribution of seropositive rats may be extremely localized within these urban environments. We surveyed four widely separated residential sites distant from the harbor within Baltimore, Maryland, USA, to determine the geographical distribution and prevalence of antibody to Hantaan-like virus in rats from urban areas of high human population density. Captured rats were weighed and examined for sexual maturity to allow some estimation of age, and their sera were examined by indirect immunofluorescent antibody assay for antibody to Hantaan virus. Seropositive rats were found at all four sites within Baltimore. Increasing antibody prevalence and high titers were associated with increasing rat weight and sexual maturity. Our results show that infection of rats by a Hantaan-like virus is widespread in Baltimore. Antibody in rats may be due to infections acquired during maturation or the delayed seroconversion of rats infected prior to weaning.