The relation between juvenile hormone (JH) released from the corpora allata of the Spodoptera  littoralis  male moths and protein synthesis in the sexual accessory glands (SAGs) of the reproductive system had been studied in the present work. The amount of total protein in SAGs of the newly emerged male moth was the lowest. It  increased as the age of the unmated male progressed to reach the maximum  in males 3 day old. Then, the amounts gradually decreased towards the end of the male life span, The highest amount was relatively similar to that found in the SAG of 3 day old male previously sham-operated and allatectomized soon after emergence. Injection of 5 µl of JH dissolved in 2 µl of olive oil per  individual S. littoralis virgin male previously allatectomized as newly emerged moths moderately increased the amounts of total protein in SAGs of 3 day old individuals. Soon after mating and separation, the male lost an average of 51.13 µg of protein in the single SAG. One day after the first mating, sex protein increased by 25.12 µg in the SAG, however, the increase in this case did not reach that in SAG of the unmated 3 day old male. After the second mating, the amount of sex protein in the same males again decreased and the compensation in protein content in SAG was very slight one day after the second mating. This indicates that the efficiency of males decreased when successive mating occurred.