The exogenous dose of 20-hydroxcy Ecdysone (20-HE) used in the present study induced an increase in the size and the secretory activity of the different types of alveoli of salivary glands in nymphet Hyalomma dromedan'r' during its developmental stages, Also, it causes salivary gland degeneration. The results suggest that the (20-HE) enhance synthesis and release of tick salivary gland degeneration factor (the degeneration factor), which is probably an ecdysteroid. (20- HE) seems to provide a stimulus for synthesis of protein. lipids and glycogen drates.