Sugarcane smut disease, caused by Ustilago scitaminea Syd. is universal in distribution being important in every sugarcane producing country including Egypt. The best control measure is the use of resistant cultivars developed by the useual breeding programmes or less common physical treatments as irradiation. In the present study, doses of Gama radiation (0.5, 1, 2, 3 kr) were used to induce mutagenesis in sugarcane buds of the commercial cultivar GT54-9. The normal and transformed percentage of smutted stools of GT54-9 mutants (257mutants) artificially inoculated (dipping and injection inoculation) with smut spores for 3 seasons were field evaluated. The mutants were grouped into 5 groups according to the transformed percentage of infection i.e, group 1 (0 -1%, 38 mutants), group 2 (>1-5%, 29 mutants), group 3 (>5-20%, 71 mutants), group 4 (>20-40%, 65 mutants), group 5 (>40%, 55 mutants). The untreated mother cultivar was placed in group 3 (5-20% infection). The results revealed the importance of direct mutagenic treatment and selection for improvement of commercial sugarcane varieties in Egypt.