Ehrlichia canis is the agent of canine Ehrlichiosis, commonly known as canine tropical pancytopenia. This canine disease is frequent in our area, as is Mediterranean Spotted Fever in humans. Recently a few cases of human Ehrlichiosis have been described in the USA. The supposed vector of both diseases is Rhipicephalus sanguineus. In order to evaluate the co-transmission of these two diseases, we selected 498 human sera positive for R. conorii and tested them for Ehrlichia canis. None of them were positive, suggesting the lack of co-transmission of the diseases.