Using a combination of fistulation, ¹⁵N isotope technique and digesta exchange between labelled and unlabelled sheep, the flow rates of digesta (Sandek et al., 2001a) and the flow rates of endogenous N (Sandek et al., 2001b) were previously estimated. On the basis of these data N reabsorption in the stomachs, the small and large intestine as well as N secretion in these three sections were calculated and differences caused by variations in the crude fibre intake of the two feeding groups (Group 1: 89.7 g/d, Group 2: 119.4 g/d) were estimated. Net N secretion into the forestomachs and abomasum varied considerably between the individual experiments (0.6-2.7 g N/d) but did not show clear differences between the groups. Daily N secretion into the small intestine was substantially higher in Group 2, amounting to 5.8 g in Group 1 and 7.7 g in Group 2 (P<0.05). In contrast, the daily N secretion into the large intestine was lower in Group 2 (2.3 g N vs 1.06 g N), corresponding to 30 and 12% of total postruminal N secretion, respectively. The daily net N absorption in the rumen and abomasum was 5.5 g N in Group 1 and only 2.9 g N in Group 2 (P<0.10). The reabsorption of postruminaly secreted N in the small intestine was 4.5 g N/d in Group 1 and 7.0 g N/d in Group 2 (P<0.05). Reabsorption per kg DMI in Group 2 were significantly enhanced when compared with Group 1 (14.7 vs 7.2 g/d; P<0.05) but there were no differences when N reabsorption was calculated as a percentage of the endogenous N entering the small intestine (77 vs 73%). Concerning N reabsorption in the large intestine (1.8 g N/d in Group 1 and 1.5 g N/d in Group 2) no differences were observed between the groups. The daily amount of postruminaly reabsorbed N was 6.4 g (Group 1) and 8.5 g (Group 2), which represents 75 and 84% of the total postruminal input of endogenous N, respectively. The greatest part of the postruminal endogenous N was reabsorbed during passage of digesta through the intestine.