Twenty-four samples of Czech pasture forages were harvested in the region of Šumava National Park and the Protected Landscape Area from three different altitudes (650, 700 and 850 m above sea level). The samples were analysed for chemical composition, in vitro digestibilities and rumen degradability of neutral detergent fibre (NDF). The effective ruminal degradability of NDF decreased with increasing altitude (P < 0.05), from 0.574 at 650 m and 0.520 at 700 m to 0.508 at 850 m above sea level. The potentially degradable fraction of NDF (b) averaged 0.774. The mean potential digestible NDF (fd, % of NDF) obtained from the long 504 hour in situ incubations were slightly higher than the b fraction. There were interactions between maturity (P < 0.0001) and altitude (P < 0.01) for b and fd. The fractional rate of degradation (c) of NDF ranged from 0.024 to 0.069, with a significant effect of harvest date (P < 0.01), but not influenced by altitude.