Leptospirosis is a disease caused by pathogenic members of the bacterial genus Leptospira. The disease has been described as the zoonosis with the widest geographical distribution. Distribution of leptospirosis is directly dependent on the local presence of carrier animals and local environmental conditions that enable leptospiral survival and maintenance outside the hosts. Official serologically based classification of leptospires depends on a two-way cross-absorption/agglutination reaction between newly isolated strains and known serovars. Leptospires are very sensitive to dryness and will die within minutes of exposure to dry conditions. The epidemiology of leptospirosis is a constantly changing dynamic process in which a shift in host-parasite relations produces variation in the relative importance of available hosts. Accumulated knowledge of leptospiral distribution and endemicity in developed countries stems from the fact that their medical and veterinary public health service personnel have been properly trained and adequately equipped to diagnose and study medical and economical damages caused by the disease.