The objective of this study was to identify genomic regions associated withpostweaning average daily gain (ADG) in swine. Two families were produced usingsires obtained from the cross of lines divergently selected for high and lowgrowth rate. Sires were mated to 29 unrelated dams that produced 124 and 115offspring. Average daily gain was recorded for every individual; mean ADG was.593 +/- .007 kg/d and .619 +/- .009 kg/d in the two families. Selectivegenotyping was performed as a prescreening procedure to identify genomic regionspotentially associated with ADG. A total of 75 genetic markers were used betweenboth families. Markers identified as nominally significant (P < .05) in anindividual marker analysis were subsequently typed in all individuals. Markersstill nominally significant (P < .05) after analysis with the complete familywere then reevaluated together with flanking markers in an interval mappinganalysis. A single region on chromosome 3, flanked by markers Sw2429 and Sw251,for the second family had a logarithm of the odds score of 2.9, which issuggestive of linkage with a quantitative trait locus for ADG. Differences were.033 +/- .009 kg/d between individuals inheriting alternative paternal allelesfor Sw251, which was the most significant marker.