SUMMARY: Our aims were to determine the seroprevalence rates for the most common types of zoonosis among the population of Extremadura (southwestern Spain) and to identify the associated risk factors. We conducted a seroepidemiological survey to collect information on family background and the habits of people residing in Extremadura between 2002 and 2003. Antibodies to Brucella were determined by Rose Bengal staining and a standard tube agglutination test; a titer of 1/80 was considered to be positive. Antibody titers for spotted fever, leishmaniasis, echinococcosis, and toxoplasmosis were determined by enzyme-immunoassays. Independent risk factors identified were age (younger age for brucellosis), male gender (brucellosis, spotted fever, and toxoplasmosis), occupation and contact with animals (brucellosis and spotted fever for those in contact with goats, hydatidosis for those in contact with sheep, leishmaniasis for those in contact with dogs, and toxoplasmosis for those in contact with cats and pigs), and consuming contaminated food (brucellosis by eating fresh cheese, hydatidosis by eating homemade sausages, and toxoplasmosis by eating pork). Except for leishmaniasis, the other zoonoses were more prevalent in rural areas, and, with the exception of brucellosis, they were all more prevalent in Badajoz. The distribution of zoonoses in Extremadura was strongly influenced by keeping livestock and eating habits. Thus, brucellosis was more prevalent in Caceres (associated with cheese consumption), while toxoplasmosis (pork consumption) and spotted fever (from hunting) were more common in Badajoz.