Objectives and Methods: To find more evidence of human exposure to Anaplasma sp in Chile, we studied 108 contacts of dogs with canine ehrlichlosis (CE) (risk group) and 61 persons without tick or CE cases contact (control group). A survey including risk factors and history of diseases compatible with chrlichiosis/anaplasmosis was applied to the risk group. Serum IgG anti-Anaplasma sp antibodies were determined in both groups. Results: A significant difference was found in the prevalence of anti-Anaplasma sp antibodies in the risk group compared with the control group (18,5 versus 3,3%), p < 0,005. No risk factors associated to seropositivity were found, nor persons with history suggesting ehrlichiosis/anaplasmosis. Ninety four percent of the houses of the risk group had tick infestation. Discussion: A greater risk of exposition to Anaplasma sp is documented in people living in close contact with CE cases and in houses with tick infestation.