Triatoma dispar Lent has been found for the first time to be naturally infected with Trypanosoma crusi. This is also the first record of the insect species in Darien Province; its range is extended into eastern Panama. The parasite isolated from Triatoma dispar was infective for laboratory mice and triatomid bugs (Rhodnius pallescens and R. prolixus) and showed the morphological and biological characteristics of Trypanosoma cruzi. Triatoma dispar readily bites man, even in daylight. The evidence suggests that the species may play an important role as the vector of Trypanosoma cruzi among arboreal animals, and may be involved in the occasional transmission of Chagas' disease to man in the jungle.