AbstractThe intestinal absorption of aluminum (Al) was studied in anin situperfusion system of rat small intestine in combination with systemic and portal blood sampling. The jejunum‐ileum was perfused with media containing 4.63, 9.25 and 18.50 mmol l−1Al chloride at pH 4.0 and 7.0. Both mucosal retention and release of Al into the blood increased at increasing perfusate concentrations. Mucosal retention was not affected by pH but at lower pH more Al was released into the blood. The amount of Al which appeared in the blood was linearly related to the mucosal retention. The Al release into the blood was much less (μmol l−1) than the mucosal retention (mmol l−1). It is concluded that the intestinal absorption of Al is pH‐ and concentration