With an estimated 12 million cases worldwide, leishmaniasis has been identified by the WHO as the least studied and least understood of the major parasitic diseases of the world. At least 350 million people are at risk. It is found in tropical and subtropical areas all over the world. The disease is widely disseminated in South America and spreading elsewhere, notably in Africa; serious outbreaks took place in India and Kenya in 1977. The disease is spreading to areas never affected before, sometimes causing epidemics of alarming proportions. Because of their zoonotic aspects, both the cutaneous and visceral forms are liable to increase with urbanization and with the reclamation of vast expanses of forest or desert, as in the Amazon basin or in the USSR. Herders and loggers have higher risks of contracting leishmaniasis. Sandflies are active during the day and are an occupational health risk to agricultural workers. Other high risk groups include workers in development projects (oil drilling, mining, road construction, and agriculture). Clearly, environmental changes brought about through human activity such as deforestation have exacerbated the public health risk of leishmaniasis. Movements of migrants, temporary labourers, and any large-scale population displacement may result in a high incidence of infection among such groups. Increasingly, tourists visiting endemic areas are reported to return infected. Among the population in endemic areas, the permanent risk of an epidemic creates constant and genuine fear. The World Health Organization estimates about 12 million cases of leishmaniasis in most parts of the world. More than 400,000 cases are reported each year. Some 350 million people in 80 countries are at risk of this disease.