The objective of the study was to compare a viscosity of water extracts of a range of commercial rye grain grown in Poland and to check if it correlates with weight of grain and protein and fibre content. In 22 samples of rye from north-eastern regions of Poland the grain weight was measured and content of crude protein determined. Samples of rye were incubated with sodium acetate buffer (WEV), or in conditions imitating in vitro digestion process - IVA (HCl-bicarbonate) and IVB (pepsin-HCl, pancreatin-bicarbonate) and viscosity of subsequent water extracts was measured. The range of obtained values was from 2.4 to 15.8 cP for WEV, from 13.6 to 240 cP for IVA and from 17.8 to 242 cP for IVB. Amongst viscosity values obtained by three methods was close correlation. They were not correlated with grain weight, but all were negatively correlated with crude protein content (r = -0.54, -0.58 and -0.62 for WEV, IVA and IVB, respectively; P<0.01). The last 2 viscosity values were also correlated with insoluble fibre content (r = 0.80; P<0.05) in rye grain.