In the southern and western sections of the United States, bites from the reduviid bug, commonly known as the kissing bug, genus Triatoma, may induce serious life-threatening allergic reactions. This study was undertaken to identify the allergens responsible for patient sensitization and to determine the extent of cross-reactivity of these allergens. The Triatoma spp. most commonly encountered in California and Arizona, T. protracta and T. rubida, were obtained, maintained in the laboratory, and dissected to prepare extracts for testing. Extracts were prepared from T. protracta and T. rubida for study by RAST, lymphocyte transformation, leukocyte histamine release, and RAST inhibition. Sera and cells were collected from patients who had generalized reactions to Triatoma bites. Our results indicate that T. protracta and T. rubida antigens to which patients are sensitized are present in extracts that contain saliva and that human responses are specific for T. protracta or T. rubida, i.e., allergic cross-reactivity could not be demonstrated.