Aluminum phosphide (Gastoxin) has been successfuly used in Brazil to control storage cereals grain insects. However it is little known, the effect of this fumigant insecticide upon the seed quality of cultivars of corn and sorghum. Two cultivars of maize (BR 105, Maya XVII) and three cultivars of sorghum (BR 005, BR 500, BR 505) were fumigated with Gastoxin, one, two and three times using two dosage levels (five and ten pellets for cubic meter). The results indicated that different levels of vigor obtained in the experiment were not affected by Gastoxin applications up to the double and three times the recommended commercial dosage.