The main aim was to determine the variation in hectolitre weight in different wheat cultivars caused by the application of several dosages (0.2, 0.5, 0.8, 1.0, 1.4, 1.7 and 2.0g/kg) of Malathion 4%. It was observed a marked and even drop in hectoliter weight from the dosage 0.2 through 1.0g/kg, but the higher dosages (1.4, 1.7 and 2.0g/kg) caused no further reduction in seed hectolitre weight. Regression equations, which were developed from these results, have shown high effectivity in correcting hectolitre weight data of Malathion-treated seeds.