The habit of chewing Qat is widely spread in Yemen. The adverse effects of the chewing Qat habit on different human body systems, namely; CNS, cardiovascular, digestive, genitourinary, and reproductive health systems were broadly investigated. Furthermore, its effect on different oral tissues including periodontal tissues, hard tissues of teeth, TMJ, muscles of mastication and salivary glands were also comprehensively reported. Since, this habit is recently highly prevalence among Yemeni Women,tTherefore, this book covers the most oral manifestations that may be occurred among Yemeni Woman due to chewing Qat.