Xenodiagnosis is a very valuable method for the etiological diagnosis of Chagas’s disease. It consists in allowing the clean insect transmitter to feed upon the suspected carrier, and in ascertaining whether the bugs become infected. The principal local vector is the most suitable species to be used in a given region. Three to six hungry nymphs are usually employed in each test and must feed until repletion (15-30 minutes). It flagellates are not detected in the faeces or in the rectal contents, obtained by anal puncture, insects are dissected 40-60 days after the <infective meal> and the duodenal contents is examined.