Human American trypanosomiasis or Chagas disease -- named after Carlos Chagas who first described it in 1909 -- exists only on the American continent. It is caused by a parasite, Trypanosoma cruzi, that is transmitted to humans by blood-sucking triatomine bugs, by blood transfusion, and transplacentally. Chagas disease has two, successive phases: acute and chronic. The acute phase lasts 6-8 weeks. After several years of starting the chronic phase, 20%-35% of infected individuals (the percentage varying with geographical area) develop irreversible lesions of the autonomous nervous system in the heart, the oesophagus, the colon and/or the peripheral nervous system. Data on the prevalence and distribution of Chagas disease markedly improved in quality during the 1980s, as a result of demographically representative, cross-sectional studies carried out in countries where no accurate information on these parameters was available. Experts had previously met in Brasilia, in 1979, and devised standard protocols for carrying out country-wide studies not only on the prevalence of human infection with T. cruzi but also on house infestation with the triatomine vectors. Thanks to a co-ordinated programme in the southernmost countries of South America (i.e.the 'Southern Cone'), transmission of T. cruzi by the vectors or blood transfusion has been successfully interrupted in Uruguay (from 1997), Chile (from 1999) and Brazil (from 2005), and the global incidence of new human infection with T. cruzi has decreased by 67%. Similar multi-country control initiatives have been launched in the Andean countries and in Central America, with the goal of interrupting all transmission of T. cruzi to humans by 2010 -- a goal set, in 1998, as a resolution of the World Health Assembly. Recent advances in basic research on T. cruzi include the genetic characterization of populations of the parasite and the sequencing of its genome.