High pressure processing was investigated for controlling Cheddar cheese ripening. One-month-or 4-month-old Cheddar cheeses were subjected to pressures ranging from 200 to 800 MPa for 5 min at 25 C. The number of viable Lactococcus lactis (starter) and Lactobacillus (nonstarter) cells decreased as pressure increased. Subsequent storage of the control and pressure-treated cheeses at 10 degrees C caused viable cell counts to change in some cases. Free amino acid content was monitored as an indicator of proteolysis. Cheeses treated with pressures > or = 400 MPa evolved free amino acids at significantly lower rates than the control. No acceleration in free amino acid development was observed at lower pressures. Pressure treatment did not accelerate the rate of textural breakdown compared with the non-pressure treated control. On the contrary, pressure treatment at 800 MPa reduced the time-dependent texture changes. Results indicate that high pressure may be useful in arresting Cheddar cheese ripening.