Calf rennet extract was prepared from minced  (A) and sliced (B) fresh vells. Yield of the rennin units in the crude extract was slightly higher in case of using the sliced vells. Adding potassium aluminum sulphate (alum) at the rate0.4% caused great decrease in pH, and rennet units /ml, whereas the sequence addition of di-sodium phosphate (0.8%) decreased the loss of rennin units from 44.18 to 1.32% in case of (A) and from 50.60 to zero%  in case of (B). The microbiological analysis of (A) and (B) extracts revealed that the total bacterial count was higher before clarification and in (A) than in (B). In all cases the extracts were free-from coliforms and molds & yeasts. During storage at room temperature (20-35 ^oC) for 3 months a slight decrease in pH of A and B extracts was recorded, whereas activity of rennet was gradually decreased in both cases. The recorded loss (%) was 29.73 and 27.72 in case of  A and B respectively at the end of storage period.