The retrograde intrabiliary injection (RII) technique was used to study the reabsorption of equimolar doses (1,2 mumol) of sulfobromophthalein sodium (BSP) and its analogue phenol 3,6 dibromphthalein disulfonate (DBSP) from the rat biliary tree under the experimental conditions established in this study i.e. variation of retrograde volumes injected and of short time cholestasis. RII was performed with a microliter syringe joined to a cannula positioned in the proximal third of the common bile duct. This technique guaranteed accurate administration of microliter quantities, also free bile flow could be reinitiated 3 - 5 sec after RII. Bile samples were collected in 2, 5 min intervals up to the 5th min, then in 5 min intervals up to the 15th min, and the following 15 min up to the 30th min and analysed for compounds administered by RII. No significant differences in the biliary reabsorption of BSP and DBSP after RII could be detected. Increasing retrograde volumes of 20, 40, 60, 110, and 160 mul lead to decreasing percent recoveries in the bile in the first 2,5 min after RII (88,0 +/- 3,8 - 15,6 +/- 3,1) when bile flow was started at once after RII. An inverse correlation between retrograde volume and percent recoveries was found. Increasing duration of cholestasis (bile flow was started at once, 0,5 min, 3 min, 6 min, and 30 min after RII) results in decreasing percent recoveries of BSP and DBSP in the first 2,5 min after free bile flow was reinitiated (52,7 +/- 3,6 - 20,0 +/- 1,2). A time dependent proportional effect could be detected. Furthermore in the case of BSP concomitant with increasing cholestasis increasing amounts of BSP - conjugates were found in the bile supporting the idea of a continuing ductular - hepatocellular circulation even during complete obstruction of the common bile duct.