A specific, fast, and easy method for revelation of active plate producers of L-asparaginase using differential medium on the basis of LB or M9 with 1.5% agar was developed. Each 100 ml of LB or M9 medium additionally contained 6-7 ml ofglycerol, 4 g of L-asparagine, 0.2 g of CaCO3, and diagnostic components: 3 ml of 0.2 M CuSO4 x 5H2O and 2.5 ml of 0.1 M K3Fe(CN)6, pH 7.6-7.8. The results were counted 12-20 or 24-48 h after strain growth at 37 degrees C in corresponding mediums. Red color of colonies and colored zone around them showed the ability of the strain under study to destroy asparaginic complexes. The recommended method allows revealing bacterial strains producing L-asparaginase with specific activity of not less than 0.1-3.0 MU/mg of protein.