ABSTRACT: Wadi Hammam Ali in Anis - Dhamar Governorate, Republic of Yemen is an upland segment valley of the major trunk valley of Wadi Rima , that generally trends NE-SW and runs south-westwards to the Red Sea. Geologically the area of Wadi Hammam Ali is situated in the Tertiary Yemen Volcanic Series of almost horizontal effusive rocks, that overlies the Cretaceous Tawila sandstones. The volcanics include ignimbrite and ash flow deposits covering considerable faul ted and fractured area, thus forming with the underline Tawila sandstones a suitable reservoir. The rhyodacite at the hot springs, as well as ryholite, dacite and trachyte, overlying the ignimbrite and the ash flow over the area, appear to act as a suitable Cap rock for the hydrothermal reservoir. Faulting is a prominent feature of the area and thus controls occurrence of springs. Geothermal activity at relatively shallow depth and the conviction of heat to the available aquifer represents the source of heat in the region due to the following: a) The prolonged history of volcanic activity since the Tertiary and Quatemary associated with rifting of the Red Sea and Gulf of Aden. b) The region is seismically active. c) The accumulating stress es in the region lead to magmatic intrusive activity.