Hernia is shown to be a serious problem in pig production, causing severe economic loss for the pig producers. The most common types are inguinal/scrotal hernia (IH) and umbilical hernia (UH). IH refers to hernial contents present in the inguinal canal an d/or that organs protrude into the scrotum. The heritabilities of IH are estimated to be very high, but no major genes or any clear pattern of inheritance have been identified. UH is defined as a hernia in which bowel or omentum protrudes through the abdo minal wall under the skin at the umbilicus (navel). The heritabilities of UH are estimated to be medium high. A recent project in our group has detected several highly significant QTLs (Quantitative Trait Loci) affecting IH in pigs, and therefore follow u p studies are highly demanded for narrowing down the QTL position in order to find causal mutations underlying the trait of interest. Samples from pigs with UH were also collected, in which we now want to perform a whole-genome scan to detect QTL affectin g UH. First we want to compare our results with those obtained in a large study on both IH and UH in Denmark in order to make sure that we are dealing with ?real? QTLs. Fine mapping of QTL will be achieved by constructing a high-resolution SNP (Single Nuc leotide Polymorphism) maps for the regions of interest combined with haplotype analysis and characterisation of candidate genes in the QTL regions. Finally, we want to use this knowledge in practical breeding to reduce hernia in pigs. This is of great imp ortance for the pig industry with respect to reducing cost and improving animal welfare Norway, and significant impact on the ability to compete on the international pig breeding market. There is great interest in this field internationally because hernia s are found in all commercial pig breeds and the problem is difficult to solve with traditional breeding strategies. Findings from this project may also be very useful for studies of hernia in human research.