Background: KIAA0319 (6p22.2) has recently been implicated as a susceptibility gene for dyslexia. We aimed to find further support for this gene by examining its association with reading and spelling ability in adolescent twins and their siblings unselected for dyslexia. Methods: Ten single nucleotide polymorphisms (SNPs) in or near the KIAA0319 gene were typed in 440 families with up to five offspring who had been tested on reading and spelling tasks. Family-based association analyses were performed, including a univariate analysis of the principal component reading and spelling score derived from the Components of Reading Examination (CORE) test battery and a bivariate analysis of whole-word reading tests measured in a slightly larger sample. Results: Significant association with rs2143340 (TTRAP) and rs6935076 (KIAA0319) and with a three-SNP haplotype spanning KIAA0319 and TTRAP was observed. The association with rs2143340 was found in both analyses, although the effect was in the opposite direction to that previously reported. The effect of rs6935076 on the principal component was in the same direction as past findings. Two of the three significant individual haplotypes showed effects in the opposite direction to the two prior reports. Conclusions: These results suggest that a multilocus effect in or near KIAA0319 may influence variation in reading ability.