Oral cholecystography is one of the most relible and widely used x-ray examination which enables us to observe not only morphological features of the gallbladder (GB) but also its functioning state. It was disclosed that functional evaluation of the GB is mandatory to recognize such kinetic disorders of the viscus as acalculous cholecystitis or dyskinesia. For the purpose of functional evaluation, fat meal has been used traditionally. Recently, cholecystokinin(CCK) and ceruletide were introduced into clinical diagnosis of the GB, the usefulness of which we have confirmed. In the present study we have made an attempt at improving cholecystagogic effect of conventional fat meals(FM) such as whole mild and egg yolk by changing the posture of the examined from sitting up to right decubitus position after the ingestion of fat meal. The hypothesis involved in this study is that the presence of quantitatively more fat meal in the duodenum per unit time may result in more effective cholecystagogic action and such a setting would be created by enhancement of pyloric passage of fat meal by decubitus posturing. Clinical materials consisted of 280 normal oral GB series (136 males and 144 females) andthey were divided into 4 equally numbered groups of mild sitting and mild decubitus and egg sitting and eggdecubitus. Upon confirming satisfactory opacification of the GB 11 hours after the ingestion of 3g of sodiumipodate or iopanoci acid either 2 pieces of medium sized hen's egg yolk were given. The xaminess were then allowed either sitting up comfortably on a bench or lying down on the right flank on a couch. After the ingestion of fat mean, x ray was taken at the end of 30 minutes in all but the mild decubitus group in which x rays were taken serially at the end of 5, 15, 30 and 60 minutes. The frontal area of each opacified GB was measured by using aplanimeter and the contraction rate before and after fat meal stimulation was calculated by the following equation and delineation of the biliary tree was analyzed in each group. Contraction rate (%) = (1 - Area of GB after FM /Area of GB before FM ) x 100 From our study it was found that assuming right decubitus position after the ingestion of fat meal resulted in marked improvement of GB contraction regardless of the type of fat meal. Eggyolk caused significantly more contraction than mild when tested in decubitus position. The maximum GB contraction occurred at end of 30 min after fat meal stimulation and cholecystogogic effect of both whole mild and egg yolk was as good as that of CCK. Delineation of the biliary three was markedly enhanced in decubitus groups as compared with sitting up groups as revealed in Fig. 3.