The discovery that certain disease states are characterized by changes
in the levels of specific tissue or cellular markers constitutes the
major driving force for radiopharmaceutical development. Although dist
inct clinical indications have not been defined for many of the recept
or-binding radiopharmaceuticals that are currently available, in vivo
radiotracer methodology (with SPECT and PET) holds great promise for t
he diagnosis of many disorders. This review summarizes advances in the
development of radiopharmaceuticals for the detection of selected rec
eptors in vivo.