This chapter deals with interpretation of data related to cardiac catheter. At the beginning there is a short discussion on normal and abnormal pressure and oxygen saturation in different cardiac chambers that may be obtained during cardiac catheterization. It also briefly describes the interpretation of this data in relation to valvular lesions or shunt anomalies. Then 16 cardiac catheterization data have been included along with questions for the students who should try to solve them by themselves. The answers are given at the end of the book.