We studied 261 ADHD probands and 354 of their siblings to assess quantitative trait loci associated with autism spectrum disorder symptoms (as measured by the Children's Social Behavior Questionnaire (CSBQ) using a genome-wide linkage approach, followed by locus-wide association analysis. A genome-wide significant locus for the CSBQ subscale addressing social interaction was found on chromosome 7q11, with suggestive signals supporting this locus on three other CSBQ subscales. We identified two other suggestive loci for the CSBQ total scale and individual subscales on chromosomes 4q35 and 7p12. Fine-mapping the significantly linked locus resulted in interesting candidate genes, although their association was not significant after permutation testing.