Colonic transit scintigraphy was developed to quantitatively evaluate colonic transit. Using this technique the progression of a radiolabeled marker from cecal instillation to defecation was studied in 7 normal male volunteers. An 8-ml bolus containing 50 mu Ci of indium 111-diethylene triamine pentaacetic acid was instilled into the cecum via a 2-mm tube, which was passed orally, and serial scintigrams were obtained over 48 h. By 48 h, 70.7% +/- 9.1% (mean +/- SEM) of the instilled activity had been defecated. The cecum and ascending colon emptied rapidly, with a half-emptying time of 87.6 +/- 27.0 min. Geometric center analysis showed an initial logarithmic progression of activity in the proximal colon and a linear progression distally. This study suggests that the transverse colon, not the cecum and ascending colon, may be the primary site for fecal storage. Colonic transit scintigraphy is a safe, physiologic, and quantitative method for evaluating the colonic transit of fecal material and may provide a useful tool for evaluating normal and abnormal large intestinal physiology.