Toxicology is a science that studies the deleterious interactions between chemicals and living organisms. This definition covers living organisms related to the problem to be analyzed: man, insects and trypanosomes. Chagas' disease, also known as American trypanosomiasis, is an endemic parasitic disease limited to the tropical and subtropical countries of Latin America (Pinto Díaz, 1984; WHO, 1981, 1985; Schirmer, Muller, and Krauthsiegel, 1995; Castro and Toranzo, 1988; Docampo and Moreno, 1985; Fairlamb, 1982). It is estimated that at least 20 million persons are infected with the etiologic agent of the disease, Trypanosoma cruzi (Pinto Díaz, 1984; WHO, 1981, 1985; Schirmer, Muller, and Krauthsiegel, 1995; Castro and Toranzo, 1988; Docampo and Moreno, 1985; Fairlamb, 1982). Further, more than 40 million are living under conditions where they may be bitten by the vector insect infected with the parasite (Pinto Díaz, 1984; WHO, 1981, 1985; Schirmer, Muller, and Krauthsiegel, 1995; Castro and Toranzo, 1988; Docampo and Moreno, 1985; Fairlamb, 1982). About 120 000 new cases per year were reported (Pinto Díaz, 1984; WHO, 1981, 1985; Schirmer, Muller, and Krauthsiegel, 1995; Castro and Toranzo, 1988; Docampo and Moreno, 1985; Fairlamb, 1982). The infection results because the vector insects (a Reduvii bug) have hematophagous habits, and because these blood sucking organisms, usually defecate immediately after having their meal. As a result, the infected feces find their way into the host bloodstream through a bite wound in the skin or via intact mucous membrane or the conjunctiva (Pinto Díaz, 1984; WHO, 1981, 1985; Schirmer, Muller, and Krauthsiegel, 1995; Castro and Toranzo, 1988; Docampo and Moreno, 1985; Fairlamb, 1982).