**Abstract**

Radiopharmaceutical material is a pharmaceutical product or drug that may exert spontaneous degradation of unstable nuclei with nuclear particles or photons emission. Radiopharmaceuticals may be used in research, diagnosis, therapy, and environmental purposes. Moreover, radiopharmaceuticals act as radioactive tracers among patients via gamma-ray emissions. Therefore, the uses of radiopharmaceuticals as diagnostic agents may be given to patients to examine any biochemical, molecular biology, physiological, or anatomical abnormalities. Therapeutic radiopharmaceutical may be administered internally for therapeutic purposes via selective effect on certain abnormal cells or organs. The best known example for therapeutic radiopharmaceuticala is iodide131 for thyroid ablation in among patients with hyperthyroid. A third class of radiopharmaceutical is drug labeling which mainly used in research by using small amount of radioactive substances not for diagnostic purposes, but to investigate the metabolism, bio-distribution, pharmakodynamic, and pharmakokinetic of certain drugs in a nonradioactive form. This chapter focuses mainly on basic fundamentals of radiopharmaceutical chemistry, preparation, environmental, pharmaceutical, diagnostic, therapeutic, and research applications.

**Keywords:** Radiopharmaceutical, Diagnosis, Environment, Research, Bio-evaluation
