We compared location, sex, and season of 97 American black bears (Ursus americanus) captured and sampled from March 2003 to March 2006 near Lakewood and Hiles, Wisconsin, USA, relative to exposure to toxoplasmosis, canine distemper virus (CDV), eastern equine encephalitis virus, Venezuelan equine encephalitis, St. Louis encephalitis, canine parvovirus, and tularemia. A large percentage of black bears in both locations had antibodies against CDV and toxoplasmosis (41.1–56.9% and 41.8–67.4%, respectively). Exposure of bears to CDV was significantly higher in those sampled during the winter. There was strong evidence that exposure to toxoplasmosis was significantly greater in bears near Hiles than those near Lakewood. There was weak evidence that exposure to tularemia was different in bears near Hiles than those near Lakewood. There was also weak evidence that exposure to tularemia was different in females than males. We found only a small percentage of black bears with detectable antibodies against eastern equine encephalitis virus, Venezuelan equine encephalitis, and St. Louis encephalitis (2.2–3.8%, 2.2–4.3%, and 0–2.8%, respectively) at both locations. Our results are similar to those of other studies, suggesting that exposure to toxoplasmosis and CDV may be prevalent among black bears across North America. We also draw attention to the need for validation studies for serological tests in black bears, so that accurate measures of sensitivity and specificity of these tests may be provided.