Bendiocarb 80WP, applied at 1 and 2 g/m2, was compared with BHC 30WP, applied at 0.5 g/m2 of gamma isomer, for the control of the important Chagas' disease vector Triatoma infestans, in Brazil. The insecticides performance was evaluated in groups of about 20 heavily infested, mud- or adobe-walled houses selected on the basis of pre-spray sample data. These houses, together with a check group of untreated, infested houses, were sampled for the presence of T. infestans pre-spray and at 1, 3, 5, 7 and 9 months post-treatment employing a systematic search technique with the aid of a flushing-out agent. This method was found to detect infestations in from 71 to 95% of the samples taken in groups of infested, untreated houses. Treatment with bendiocarb 80WP at 2 g/m2 resulted in the elimination of T. infestans from 40 to 50% of the infested houses, whereas BHC 30WP at 0.5 g/m2 reduced the number of infested houses by 70–80%. In the houses where the bugs were not eliminated the populations were markedly reduced in size by the insecticides, but became reestablished by 5 months post-spraying. Detailed analysis of the field trial sample data together with the results of a simple laboratory experiment suggest that although bendiocarb WP powder may be intrinsically more toxic to triatomines than BHC WP, it is less persistent when applied in house largely constructed of mud.