Collections of triatomine bugs inhabiting inside dwellings at villages of two prefectures in Guatemala were carried out and 293 individuals of Rhodnius prolixus and 170 individuals of Toriatoma dimidiata were obtained, both of which are the main vector species of Chagas' disease in Guatemala. Of these, 202 (68.9%) of R. prolixus and 157 (92.4%) of T. dimidiata were engorged. Blood meal analysis with ELISA revealed that the sources of 97 blood meals (48.0%) of R. prolixus which were identified to be human (28.2%), followed by chicken (7.9%) and opossum (7.4%). Eighty two blood meals (52.2%) of T. dimidiata and they were to be human (30.6%) followed by opossum (15.3%) and cow (7.0%). Multiple feedings were observed 12 blood meals (12.4%) of R. prolixus and 16 (19.5%) of T. dimidiata. It turns out that triatomine bugs inhabiting inside of the dwellings in Guatemala prefer human most as the blood source.