Methemoglobin toxicities of primaquine and compound N1-(3-acetyl-4-5-dihydro-2-furanyl)-N4-(6-methoxy-8-quinolinyl) 1, 4-pentanediamine, CDRI Code 80/53, have been compared in beagles. Primaquine administration at 3 mg/kg for 7 days produced significantly high (P < 0.001) methemoglobinemia and the levels increased 10.55-fold. Compound 80/53 at 3.75 mg/kg × 7 days produced a marginal increase in methemoglobinemia (3.24-fold; P < 0.02). The methemoglobin formed by primaquine administration was 3.65-fold (P < 0.001) higher than that formed after administration of compound 80/53. There was no significant change in other hematological parameters and liver function tests.