Ehrlichia canis (E canis) is the principal cause of canine monocytic ehrlichiosis (CME) and the only Ehrlichia spp that has been identified in the dogs of Europe. 1 Clinical recovery is the expected outcome of acutely infected dogs entering the subclinical phase, which could last several months to years; however, an unpredictable proportion of dogs will eventually develop the chronic phase, typically characterized by aplastic pancytopenia and a high mortality. 2 Fever, depression, anorexia, lymphadenomegaly, splenomegaly, mucosal pallor, ocular abnormalities, bleeding tendencies, and thrombocytopenia or bi-pancytopenia are common clinical and hematologic findings in CME. 1,2 The indirect fluorescent antibody (IFA) test and several in-clinic assays have enabled the comprehensive evaluation of exposure to E canis in dogs living in or traveling across endemic areas. 3 Several Abstract Background: Ehrlichia canis (E canis) infection has been documented in a few small canine case series in Greece. However, there is limited information on the prevalence of exposure to, or the potential risk factors associated with E canis seroreactivity in a large native canine population. Objectives:The objectives of this study were to evaluate E canis seroprevalence in dogs admitted to a veterinary teaching hospital, and to investigate the potential association between seropositivity and signalment, health status, the serologic assays used, and selected clinical and clinicopathologic abnormalities. Methods:The medical records of 850 client-owned dogs, tested using three in-office serologic assays, were retrospectively reviewed. Results:The E canis seroprevalence was significantly higher in sick (54.9%) compared with healthy (33.9%) dogs. Seropositivity differed significantly between the serologic assays used in this study (ImmunoComb vs SNAP 3Dx/SNAP 4Dx). Dogs presenting with bleeding tendencies, anemia, thrombocytopenia, leukopenia, pancytopenia, and hyperproteinemia were more likely to be E canis seropositive, and the median hematocrit (HCT), white blood cell (WBC), neutrophil, and platelet values were significantly lower in seropositive compared with seronegative dogs. Conclusions:A high E canis seroprevalence was documented in a canine population living in an endemic area. Selected clinicopathologic variables might be useful indicators of E canis exposure and could allow the prioritization of serologic testing in the clinical setting. K E Y W O R D Sdog, monocytic ehrlichiosis, serology