Costs associated with the clinical use of positron emission tomography (PET) at the Mallinckrodt Institute of Radiology are analyzed according to the two major components: radiopharmaceutical production and imaging. Estimated annual costs are +584,500 for PET radiopharmaceutical production and +644,250 for PET imaging (1982 U.S. dollars). The economic break-even point charge to cover expenses is +615-+2,780 per clinical procedure, depending on several variables, especially procedure volume. Charges for PET clinical procedures will be among the highest of all charges for diagnostic imaging procedures, perhaps even higher than these estimates at some institutions. Several technologic and procedural approaches to reducing costs are suggested, the most promising being the anticipated availability of positron-emitting radionuclides from commercial suppliers.