Laboratorical investigation were conducted to know the effect of irradiation (sterility) onrnreproductive performance of females G. pallidipes mated with sterile and fertile malesrnunder temperature of 23-25 oC and 75-80% relative humidity. Completely randomizedrndesigns with three replications were followed throughout the experiments.rnThe irradiation effects on male G. pallidipes at different doses of irradiation were checkedrnusing, 60Gy, 80Gy, 100Gy and 120Gy. Results showed that at highest doses the sterilityrneffects on male Glossina pallidipes were significantly lower than lowest doses (P< 0.05) onrnpupae production and emergence of adults. On the other hand, the highest dose (120Gy)rncaused abortion of egg/larvae significantly higher than the lower dose (60Gy) (P< 0.05). Inrnother investigation which was aimed to assessing the competitiveness of sterile males tornfertile males in a cage at ratios of 9 sterile: 1 fertile males, 7 sterile to 3 fertile males, 5rnsterile to 5 fertile males and 3 sterile to 7 fertile males, the results showed that the ratio withrnthe highest number of sterile (9: 1) in the cage caused significantly low number of pupaernand number of adults emerged from pupae than those with lower number of sterile males (3:rn7) (P< 0.05). Similarly, the ratio with the highest sterile males (9: 1) resulted in significantlyrnhigher number of egg/larvae abortion than those with lower number of sterile males (3: 7)rnratio (P< 0.05). In the present study, survival of male G. pallidipes irradiated with 120Gyrnthree days after emergence from pupae was significantly higher than males irradiated onernand ten days after emergence from pupae (P< 0.05). This may indicate that irradiated malesrnmay need to rest up to 7 or 10 days before released to the field. The importance ofrnsterilization using appropriate dose, the appropriate ratio of sterile to fertile males and therntime at which sterility was done efficiently all are relevant.