Studies were carried out in order to determine the dynamics of changes in lysozyme activity in the serum of turkey females during the laying period, and to identify the relationship between lysozyme activity and utility parameters. The experiments were carried out on 107 randomly chosen females from a maternal female strain (J-44), selected to increase egg production. Lysozyme activity was determined four times, in the 6th, 12th, 18th and 24th week of the laying period. Lysozyme activity was found to increase significantly in the 12th week, followed by a subsequent, gradual decrease. In the 18th week of the laying period, a significant negative correlation was found between lysozyme activity and the number of laid eggs and hatchabihty, and a significant positive correlation between lysozyme activity and percentage of unhatched poults. Correlation between lysozyme activity and reproductive performance in other periods was low and insignificant.