Objectives : The serotonin transporter gene(SLC6A4) is one of the most widely studied candidate genes in autism spectrum disorder(ASD), but there have been conflicting results from studies into the association between SLC6A4 and ASD. The aim of this study was to evaluate the association between single nucleotide polymorphisms(SNPs) in the SLC6A4 gene and ASD in the Korean population. Methods : We selected 12 SNPs in SLC6A4 and observed the genotype of 151 Korean ASD trios. We tested the family-based association for each individual polymorphism and haplotype by using the standard TDT method in Haploview(http://www.broad.mit.edu/mpg/haploview/). Results : Through transmission-disequilibrium testing and haplotype analysis, we could not find any statistically significant transmitted allele or haplotype. In addition, a case-control association test with Korean HapMap data did not reveal any statistical significance. Conclusion : Although serotonin-related genes must be considered candidate genes for ASD, we suggest that common SNPs of SLC6A4 are not important markers for associations with Korean ASD.