Hexane extracts of volatile substances collected as an air current passed through a glass chamber containing adult females and males of Triatoma mazzottii Usinger showed a male-attracting pheromone. A hexane extract from the abdominal walls of female and from aqueous female feces attracted males to females; the aqueous extract may be a different pheromone or a combination of a sex and aggregation pheromone. No difference occurred in the attraction response for fed and unfed males. Sex pheromones obtained from females of T. mazzottii also had a positive effect on virgin males of T. pallidipennis (Stahl) and T. barberi Usinger, suggesting interspecificity. Virgin males of Rhodnius prolixus Stahl and Dipetalogaster maxima (Uhler) were less attracted to the pheromone. Evidence suggests occurrence of at least two other aggregation pheromones: one in both nymphal and adult female feces that affects only unfed adult females and nymphs, and another present in male feces that affects fed or unfed males. Inglés