A quantitative trait locus (QTL) analysis of growth and fatness data from athree generation pig experiment is presented. The population of 199 F2 animalswas derived from a cross between wild boar and Large White pigs. Animals weretyped for 240 markers spanning 23 Morgans of 18 autosomes and the X chromosome.A series of analyses are presented within a least squares framework. First,these identify chromosomes containing loci controlling trait variation andsubsequently attempt to map QTLs to locations within chromosomes. Thispopulation gives evidence for a large QTL affecting back fat and another forabdominal fat segregating on chromosome 4. The best locations for these QTLs arewithin 4 cM of each other and, hence, this is likely to be a single QTLaffecting both traits. The allele inherited from the wild boar causes anincrease in fat deposition. A QTL for intestinal length was also located in thesame region on chromosome 4 and could be the same QTL with pleiotropic effects.Significant effects, owing to multiple QTLs, for intestinal length wereidentified on chromosomes 3 and 5. A single QTL affecting growth rate to 30 kgwas located on chromosome 13 such that the Large White allele increased earlygrowth rate, another QTL on chromosome 10 affected growth rate from 30 to 70 kgand another on chromosome 4 affected growth rate to 70 kg.