A dichotomous key is proposed for the identification of eight species of Clostridium: Clostridium botulinum, C. butyricum, C. haemolyticum, C. histolyticum, C. paraperfringens, C. perfringens, C. sporogenes y C. subterminale, on the basis of the Gram staining, catalase production, growth on nutrient agar, glucose utilization, motility test, gelatin hydrolysis, lecithinase production, human blood hemolysis and the test of mice toxicity.