The effect of seeding operation on the dynamic strength of urea prills is investigated in a large scale urea production unit of a petrochemical plant. According to the experimental results the mean dynamic strength of 88%wt weel above the recommended value of 85%wt can be obtained if a seed composition of 450 ppmw with the mean size of 20 micrometer is used for seeding operation. A semi empirical correlation for description of the seeding process is also presented. The predicted prill dynamic strength is always within +_2.2% of the measured value.