Radionuclide ventriculography is a relatively simple, easily repeatable technique for the noninvasive assessment of global and regional ventricular function. Since the initial description of radionuclide ventriculography over 15 years ago, it has found widespread application in the diagnosis and evaluation of patients with coronary, valvular, myopathic, and congenital heart disease. This manuscript, the first of two parts, reviews the technical aspects of radionuclide ventriculography, including both gated equilibrium and first-pass methods. The available radiopharmaceuticals, the necessary equipment, and the most reliable procedures are described. The strengths and weaknesses of both methods are compared, including their relative resolutions, the acquisition times required, the variables that may be measured, and the repeatability of each. Finally, the most recent development in radionuclide imaging of the cardiac blood pool, gated tomographic imaging, is described, and its potential clinical applications and advantages are discussed.