Quality control as regards nuclear medicine heart studies refers to two areas: methodological quality control clinical quality control. Methodological correct realization of nuclear medicine heart studies is the first prerequisite for validity of the results. The term "myocardial scintigraphy" summarizes several different procedures. Concerning clinical routine, myocardial scintigraphy stands for imaging of microcirculation and scars using Tl-201-chloride or Tc-99m-MIBI, additionally for metabolic assessment of myocardial viability with F-18-FDG. Today, planar myocardial scintigraphy has been replaced by tomographic techniques (SPECT, PET). Methodological procedures for quality control concerning technical equipment and radiopharmaca are based on the new "guidelines for radiation exposure in medicine" of 1993. Clinical quality control in myocardial scintigraphy covers, in particular, the correct selection of indications: proof/exclusion of coronary artery disease (depending on prevalence) specific questions before interventional therapy (myocardial ischemia, myocardial viability) follow-up and therapy control. Selection of the procedure for myocardial scintigraphy depends on the clinical question. However, different methodological strategies are under discussion. Adequate preparation of the patient and realization of the investigation (withdrawal of medication, selection of type and intensity of stress) are prerequisites for valid results. Interpretation has to consider that myocardial scintigraphy represents different parameters than, for example, coronary morphology. False positive as well as false negative results can occur due to methodological and biological causes. Optimization of methodological and clinical quality control in nuclear medicine heart studies requires a close and competent co-operation of cardiologists and nuclear medicine physicians.