Chagas' disease is an endemic parasitic disease and constitutes an important health problem in Latin American countries. The increasing number of immigrants from these countries has resulted in a rise in diagnosis and consequently in the treatment of this disease in developed countries not familiar with this condition. Currently, benznidazole is used for treatment of this condition. However, undesirable effects have been reported with this treatment, and there are few data about continuous long-term use of this drug. We describe a case of invalidating pain syndrome in a 31-year-old Bolivian woman with Chagas' disease while receiving benznidazole therapy. Because of the number of cases with this condition will probably increase because of immigration, a better understanding of the side effects of the treatment of this disease is essential.