We investigated potential effects of parent-of-origin specific quantitativetrait loci (QTL) in chicken. Two divergent egg-layer lines differing in eggquality were reciprocally crossed to produce 305 F2 hens. Searching the genomeusing models with uni-parental expression, we identified four genome-widesignificant QTL with parent-of-origin effects and three highly suggestive QTLaffecting age at first egg, egg weight, number of eggs, body weight, feedintake, and egg white quality. None of these QTL had been detected previouslyusing Mendelian models. Two genome-wide significant and one highly suggestiveQTL show exclusive paternal expression while the others show exclusive maternalexpression. Each of the parent-of-origin specific QTL explained 3-5 % of thetotal phenotypic variance, with the effects ranging from 0.18 to 0.4 phenotypicSD in the F2. Using simulations and further detailed analyses, it was shown thatdeparture from fixation in the founder lines, grand-maternal effects (i.e.mitochondrial or W-linked) and Z-linked QTL were unlikely to give rise to anyspurious parent-of-origin effects. The present results suggest that QTL withparent-of-origin specific expression are a plausible explanation for somereciprocal effects in poultry and deserve more attention. An intriguinghypothesis is whether these effects could be the result of genomic imprinting,which is often assumed to be unique to eutherian mammals.