A study was conducted in the experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh during November 2012 to April 2013 in order to find out an effective dose of cypermethrin insecticide (that is commonly used in Bangladesh) against Eggplant Shoot and Fruit Borer (ESFB). Including control there were five treatments were used to measure the effectiveness of the particular insecticide based on fruit infestation, total yield and also benefit - cost ratio. Among the different treatments Ripcord (cypermethrin) 10 EC @ 1 ml/l of water sprayed after observing 5% level of fruit infestation and repetition of the same at 15 days interval (T3) performed the best in respect of marketable yield (30.55 t/ha), reduction of fruit infestation over control (77.54%) and also the benefit cost ratio (8.14).