Insectivores (Erinaceus europaeus) and rodents (Rattus rattus, R. norvegicus and Mus musculus) from different islands of the Azores Archipelago were found to carry three distinct Leptospira interrogans s.l. serovars (copenhageni, icterohaemorrhagiae and ballum) which have never been previously investigated there. The house mouse and the black rat were the major Leptospira reservoirs showing isolation rates ranging from 0% for both species (in Graciosa) to 88% and 33%, respectively (in Sãao Miguel). This study also showed that the majority of the animals with positive kidney cultures exhibited specific agglutinins against the isolated strains of Leptospira. The observed isolation rates in the different islands, with a very interesting island variation in prevalence, suggest that small mammals, serving as sylvatic reservoirs of pathogenic leptospires, may represent an important risk to the health of humans and livestock, particularly in the islands of Terceira and Sãao Miguel.