Abstract Radionuclide angiography (RNA) has played an important role in the evaluation and management of patients with heart disease, particularly those with CAD, chemotherapy-related heart disease, secondary pulmonary hypertension, and known or suspected intracardiac shunts. Its application has waned over the years, largely due to advances in cardiac ultrasound and cardiac MRI. However, practitioners of nuclear cardiology should continue to advocate for the technology and should train themselves, if necessary, teach others, and apply this robust technique in the appropriate circumstances. To date, no measurement from any other technique has surpassed the power of the first-pass RNA peak exercise LVEF for predicting cardiac death in patients with known or suspected stable CAD. Equilibrium RNA offers the unique, direct relationship between recorded counts in a chamber and the volume of that chamber. It is that relationship that makes ERNA an accurate and reproducible method for assessing systolic and diastolic function. It is considered superior to 2D echo for measuring LVEF and RVEF and should remain a test of choice for patients in whom an exact LVEF is critical, such as those being considered for an implantable defibrillator. Shunt detection and quantitation are strengths of FPRNA, and the study can be performed quickly and inexpensively with little operator interaction. Shunt quantitation is difficult with echocardiography and more time-consuming, more expensive, and less readily available with MRI. This chapter provides the information and references to essential literature that will introduce readers to or refamiliarize them with the rationale, technical aspects, and applications of RNA.