The effect of adding 0.5, 1.0, and 2.0 AU l(-1) of the cysteine proteinase from Micrococcus sp. INIA 528 to pasteurized ewe＇s milk on the acceleration of Manchego cheese ripening was investigated. Whey dry matter and protein content were higher for experimental cheeses than for control cheese. Residual alpha(s)-casein was significantly lower in experimental cheeses than in control cheese from day 30 and residual beta-casein from day 15. Hydrophobic peptides, hydrophilic peptides, their ratio and N soluble in phosphotungstic acid were significantly higher in experimental cheeses than in control cheese from day 15. Experimental cheeses showed a less firm texture with lower values for fracturability, elasticity, and hardness from day 30 due to their more pronounced proteolysis. Flavor quality was improved by cysteine proteinase addition to milk, and no differences between bitterness scores of experimental and control cheeses were recorded Flavor intensity was enhanced by enzyme addition to milk from day 15. Manchego cheese made from milk with 2.0 AU l(-1) cysteine proteinase would reach in 36 days the flavor intensity of 60-day control cheese.