Serological investigations of small mammals had been made on the Island Santiago (Cape Verde Islands), to clear up how far synantropic, small mammals are reservoir hosts for pathogens, such as Coxiella burnetti and Listeria monocytogenes. 367 small mammals representing two species (Rattus rattus and Mus musculus) were trapped. Q-fever antibodies were detected in 155 of 350 examined rats and mice (44.29%). 18.89% of all tested sera showed positive results to Listeria-antigen, serovar 4bH, 5.48% to 4b0 and 9.75% to 01.