The influence of replacing cellulose in a casein diet with oligosaccharides from lupin and pea seeds (diets LOS and POS, respectively) on the metabolism of the caecum was investigated in an experiment on Wistar rats. The experimental diets contained 3.89 or 4.87% α-galactosides and 2.8 or 2.0% sucrose (LOS and POS, respectively). In rats receiving the diet with oligosaccharides, a greater weight of digesta and caecal tissue (especially in the LOS group), as well as a higher pH (range 7.15-7.37) and ammonia concentration (46-51 mg/100 g) in the caecal content were recorded, compared with the control group (7.03 and 24 mg/100 g, respectively). In rats fed diets with oligosaccharide extracts, the dry matter of caecal digesta was significantly lower and activities of bacterial β- and α-galactosidase, α-glucosidase and β-glucuronidase were significantly higher. The concentration of short-chain fatty acids in the caecum digesta was higher in rats given pea oligosaccharides (129.16 µmol/g fresh digesta), than in rats fed with lupin-extract (98.55 µmol/g) and rats fed the diet with cellulose (112.58 µmol/g). Compared with cellulose, the total production of SCFAs in the caecum (expressed as µmol/100 g BW) was significantly higher when the diet contained 4.87% α-galactosides from pea (POS-group) and insignificantly higher when the diet contained 3.89% of lupin α-galactosides (LOS-group).