Leptospirosis is a zoonotic spirochetal disease of global importance. This disease continues to have a major impact on people living in urban and rural areas of developing countries with inestimable morbidity and mortality. Funding for research and control efforts is currently haphazard, not organized and not effective for public health efforts, primarily because there are no concerted, ongoing international efforts to assess the impact of leptospirosis on human health. Major issues in the field need to be addressed to develop strategies of control, amelioration and treatment. These include the following: mechanisms of naturally acquired and vaccine-induced protective immunity against clinical leptospirosis; mechanisms of severe leptospirosis pathogenesis; standardized, precise and simplified taxonomy of Leptospira relevant to disease manifestations, transmission and control; effective adjunct treatments in addition to antimicrobials; and environmental assessment for risk of leptospirosis transmission and relevant mammalian reservoirs. Once effective ongoing, collaborative international efforts to assess the impact of leptospirosis on human and veterinary health are underway, appropriate mobilization of clinical and public health research funding will follow.