Ruminal degradation of crude protein from feedstuffs was determined in steers that were fed diets based on either maize (whole, meal or flakes) or on by-products of the milling industry. In addition to the in sacco degradation study, fractional outflow rates of Cr-mordanted fish-meal particles were studied at DM intakes between 0.04 and 0.12 kg/kg WO,75/d. Predicted crude protein degradation was calculated at rate constants for outflow of 0.04 and 0.06/h respectively. The rate constant for outflow was correlated with level of DM intake (r2 = 0.87). Lag phase prior to degradation of crude protein of cottonseed oilcake meal differed significantly with diet of the host animal (whole maize vs. maize meal and flaked maize), but the predicted extent of degradation did not differ significantly. The predicted extent of degradation of crude protein was higher for maize meal than for whole or flaked maize. Extent of crude protein degradation of other selected feedstuffs was not significantly different between two replicate periods of measurement and ranged from a low of 29.8% at a rate constant for outflow of 0.06/h for gluten 60 to a high of 87.3% for wheat bran.