In vivo drug release and ateorption in the gastrointestinal tract are governed by a complex process subject to many variables. Extensive efforts were spent in studying the durg and manipula ting the excipient and mechanical design of the formulation but little is known regarding the physiological factors that influence the release and absorptive processes.Understanding of the behavior of formulation inside the GI tract has been made by gamma scintigraphy using a single isotope. However, the technique is suffering from several limitations : (1) anatomical location of the object is difficult to determine; (2) quantification of radioactivity is difficult due to tissue attenuation and movement of isotope; (3) cannot distinguish between a radionuclide present as a solid or as a solute; (4) preparation of the radiolabeled dosage forms are pro-blematic; and (5) neither the drug nor the excipients can be labeled with nuclide. These problems can be partly alleviated by using dual isotopic, geometric mean measurement, perturbed angular correlation, neutron activation, and pharmacokinetic techniques. Combining several scintigraphic techniques with pharmacokinetics can drastically improve the quality of the data, Thus, the term pharmacoscintigraphy was coined. The application of pharmacoscintigraphy can be further supplemented by other techniques such as stable isotope with gas chromatography-mass spectrometry, pH monitoring and gastrointestinal intubation. Those techniques can be used either independently or simultaneously with pharma-coscintigraphy to provide us with a full picture of durg release and absorption in humans.