Wildlife species can serve as biomonitors of environmental health and are prognostic of ecotoxicological consequences when contaminants are introduced into the environment. Small mammals, particularly rodents, comprise the majority of indicator species used in terrestrial biomonitoring studies; however, many biomonitoring studies address acute effects over relatively short periods. We still know little regarding effects of chronic exposure to contaminants on small mammals. The overall goal of this study was to determine ecological characteristics of small mammal communities inhabiting a heavy metal contaminated site, Tar Creek Superfund Site, compared to reference sites located in northeastern Oklahoma over a 2 y timeframe. Primary hazardous materials present at Tar Creek Superfund Site include lead, zinc and cadmium. Mark-recapture techniques were employed to test the hypothesis that structure and composition of small mammal communities inhabiting this contaminated site would be significantly altered compared to uncontaminated reference sites. Contaminated and reference sites were similar in vegetation compositional characteristics. Small mammal communities inhabiting Tar Creek Superfund Site had reduced species diversity, including richness and evenness, compared to reference sites. Furthermore, communities within Tar Creek Superfund Site were dominated by a single species, Peromyscus leucopus (white-footed mouse). Species composition was different between contaminated sites and reference sites as evidenced by detrended correspondence analysis, with contaminated sites being more similar to each other than to either reference site. No direct link between site contamination and disparities among most ecological characteristics could be established.