Interpretation of i-UDS tracings follows certain general principles. This chapter elucidates the salient points to be considered while reading i-UDS traces starting from basic identification of different lines in a trace and proceeds further by describing the different physiologic and pathologic findings. A checklist is provided to cover all the points. The theoretical aspects are supplemented with numerous charts and figures. Special stress has been given on physics of voiding and analysis of pressure-flow relationship during voiding. The pitfalls of pressure-flow analysis have also been mentioned.