Unreinforced masonry (URM) buildings occupy significant portion of building stock in earthquake prone areas of the world. Many building codes as well as FEMA 356 allow implementation of performance based concepts on these buildings. The work presented in this book is about performance assessment of URM buildings through a new nonlinear equivalent frame modeling technique. After reliability of the model is tested with a reversed cyclic and a dynamic shake table tests, it is applied to existing buildings. Pushover and nonlinear time history analyses of three unreinforced brick masonry buildings which are damaged in 1995 earthquake of Dinar (Turkey) is conducted and performance assessment of the buildings are made. Application of the proposed model is easy to apply with commonly used analysis programs. Thus, the book would be helpful for engineers designing and assessing URM buildings as well as for civil engineering/architecture students interested in the subject.