Cane molasses is extensively used as an energy source for cattle because of its high content of water soluble carbohydrates. However, its very low crude protein content and its ability to reduce non-protein-nitrogen (NPN) utilisation in ruminants in comparison with cereal grains may restrict its inclusion in dairy cow rations. Adding vegetable protein or urea to a cow ration containing high levels of molasses may therefore result in a better match between the nitrogen and energy requirements of rumen microorganisms. A previous experiment showed that lactating dairy cows could be fed molasses in a grass silage-based complete diet up to 312 g/kg DM without adverse effects (Yan and Roberts, 1992). The present experiment was subsequently undertaken to evaluate the responses of lactating dairy cows to protein levels in complete diets containing this high level of molasses