Skim milks were concentrated by ultrafiltration. Cream was added to the retentates to give cheesemilks standardized to a casein: fat ratio of ∼ 0·74 with protein levels ranging from 30 to 46 g/1. Pasteurized cheesemilks were renneted on a volume basis (22 ml single strength calf rennet/100 1) and converted to Cheddar cheese in 500 1 cheese vats. Set temperatures were reduced from 31 to 28 °C with increasing milk protein level to normalize curd firming rates and prevent curd shattering on cutting the curds. Cheesemaking was otherwise as normal for Cheddar cheese. The proportions of milk fat and protein lost in the cheese whey were not significantly influenced by milk protein level. Moisture-adjusted cheese yields increased with milk protein at a rate similar to that predicted by the Van Slyke cheese yield equation. However, owing to the negative correlation between cheese moisture and milk protein concentration, actual yields increased at a lower rate with respect to milk protein than moisture-adjusted yields. Increasing milk protein levels resulted in significant (P < 0·01–0·001) decreases in the concentrations of moisture, moisture-in-non-fat cheese solids and fat-in-dry matter in the cheese and increases (P < 0·05–0·001) in the levels of protein, salt-in-moisture, Ca and P. While increasing milk protein concentration resulted in significant (P < 0·05–0·01) reductions in the levels of water-soluble N at all stages of the 270d ripening period, it had little influence on the sensory scores awarded for aroma/flavour at 180 or 270d.