In this Technical Note, the quantitative turbidimetric assay for determination of the bacteriolytic activity of enzymes with gram-negative bacteria is proposed. The reactivity of hen white-egg lysozyme toward gram-negative E. coli intact cells was studied. It was found that the highest lysis rate occurred at pH 8.9 in the system containing 0.03 M NaCl. The mechanism of the reaction is discussed and applied for the quantitative evaluation of the reaction rate. The proposed method enables fast, reliable, and reproducible analysis of bacteriolytic activity of lysozyme with gram-negative bacteria.