Today, Triatoma sordida is the most frequently captured triatomine in Brazil. For a better understanding of its vectorial potential, its feeding dynamics and dejections behaviour were studied in comparison with Triatoma infestans and P. megistus. The proportion of T. sordida and T. infestans that blood fed on anaesthetized rats did not differ significantly. There was no significant difference in the time elapse between release of the bugs and the initiation of blood feeding. The mean time between completion of a blood meal and the first dejection was significantly lower in T. infestans than in T. sordida. The numbers of insects that defecated during the blood meal or immediately afterwards was similar for both species. Approximately 80 specimens of each of T. sordida, T. infestans and Panstrongylus megistus were offered daily blood meals for 30 minutes, over a period of 30 days. T. sordida bit more frequently than did P. megistus and T. infestans. These data could indicate that T. sordida may not be completely adapted to its host and might have difficulty in complete its blood meal.