Abstract: Expected progeny difference (EPD) is a sort parameter which provides estimation of the genetic value of an animal as a parent based on theory of BLUP. EPD value is a half of estimated breeding value, which is understood easily. It directly reflects breeding value from animal. Specifically, EPD is main index for genetic merit differences between two individuals from the same breed. So it can predict performance differences between their offspring if they are mated to animals having average genetic merit. EPDs are calculated for birth, growth, maternal, and carcass traits and more traits with animal performances. EPD has been broadly applied in sire evaluation. The results of EPD estimation for individual are easily been published or announced on internet and (or) intranet. The producer can select their favorite bulls according to their own requirements. The paper will give details about the principles and applications of EPD.

Key words: EPD; BLUP; EBV; traits; beef bull