The residual of calf (CR) and microbial rennet (MR) in curd playing a role in cheese ripening, depending on quantity of residual rennet retained in the curd – The effect of CaCl₂, NaCl, pH and rennet concentration on retention of rennet was studies. The results indicated that: 1)-Increasing of CaCl₂ concentrations up to 0.05% showed increasing of residual CR and MR in the curd and decreasing for whey except that of CR in the curd from buffaloe's milk. 2)-Increasing of NaCl concentrations showed a reduction of residual CR and MR in the curd and whey from buffaloe's and cow's milk. 3)-Reducing pH of milk showed an increase in retention of CR and MR in the curd from buffaloe's and cow's milk, and reduced the retention rennet in the whey from both buffaloe's and cow's milk. 4)-Increasing CR and MR concentrations as a percent appeared significant differences in the residual rennet between treatments except curd from cow's milk.  Also the increasing of CR and MR concentrations as a mount of rennet unit showed increasing of residual rennet in the curd and whey from buffaloe's and cow's milk.