The medical cyclotron has been used for the production of various short-lived, positron emitting radionuclides including carbon-11, nitrogen-13, oxygen-15, and fluorine-18. The carbon-11 alpha-amino acids are generally prepared by reacting either precursor ketones or aldehydes with potassium cyanide in the presence of ammonium carbonate at high temperatures in sealed steel reaction vessels, with subsequent hydrolysis of the intermediate hydantoin using aqueous base. Carbon-11 amino acids have been developed as in vivo organ and tumor imaging agents. In particular, the pancreas has been studied using both natural and synthetic amino acids. It is becoming clear that amino acid utilization plays a vital role in tumor growth. Alteration in amino acid transport may be a useful parameter for both diagnosing and monitoring malignant growth. Carbon-11 amino acids have potential as organ and tumor imaging agents, as well as for the study of in vivo amino acid biochemistry.