Background & objectives: Leptospirosis has been repeatedly reported from the State of Kerala since 1989 and is one of the commonest diseases among the 14 notifiable diseases in the district level communicable disease surveillance system. As there are no field studies on human leptospirosis in Kerala, we undertook this seroepidemiological study of ieptospirosis in the two hamlets of Ernakulam district in Kerala to identify locally prevalent serogroups, and to understand local epidemiological features of the disease. Methods: Blood samples were collected for five consecutive years from persons willing to subject themselves for the study from the selected areas (Kunnackal and Kunnakkurudy hamlets). Animal studies were conducted among samples from rodents captured from the area by the human volunteers themselves. Antibody titres were determined by microscopic agglutination test (MAT). The investigators inspected all the houses and surrounding land of the study subjects in this period.