Hydrophobic and hydrophilic peptides in the water-soluble fraction of 20 batches of Hispanico cheese made from pasteurized and raw milk were determined by reversed-phase HPLC, with detection at 214 and 280 nm. Cheese flavour characteristics were evaluated by a sensory panel, and regressions of bitterness scores on levels of hydrophobic and hydrophilic peptides and their ratio were calculated. The best fitting relationship for pasteurized milk cheese was the linear regression of mean panel bitterness scores on hydrophobic peptides at 280 nm (r2=0·791). The determination coefficient for the regression of hydrophobic peptides at 280 nm on panellist bitterness scores (r2=0·356) was lower, owing to individual differences in the perceived intensity of bitterness. In the case of raw milk cheese, the respective determination coefficients were 0·203 for panel scores and 0·034 for individual panellist scores.