An animal model was developed for the genetic evaluation of semen traits of pig dam and sire breeds. Fixed effects in the animal model were: month of collection, age of the boar at collection, interval between subsequent collections, combined effect of AI centre and year and breed or crossbred combination. The permanent environmental effect of the boar and the additive genetic effect of the boar were treated as random effects. Data were from all AI centres in the Czech Republic; the ejaculates were collected from 2000 through 2007. Traits considered per ejaculate were semen volume, sperm concentration, motility, percentage of abnormal sperm, total number of sperm, and number of functional sperm. Semen volume showed the highest heritability (near 0.30) and the heritabilities for the remaining traits were in the range from 0.10 to 0.20. High negative genetic correlations were observed between semen volume and sperm concentration and between motility and percentage of abnormal sperm.