Genetic studies on SIDS have been motivated by clinical, epidemiological, and/or neuropathological observations made of SIDS victims. One of the candidate genes is the serotonin transporter (5-HTT) gene, based on decreased serotonergic receptor binding observed in the brain-stems of SIDS victims. Two polymorphisms in the regulatory region of the 5-HTT gene differentially modulate gene expression (promoter, intron 2). The promoter allelic variants long (L) and extra long (XL) and the intron 2 12-repeat allele seem to be associated with SIDS; however, the 5-HTT promoter allele distribution varies widely by ethnicity. We investigated the DNA of 145 Caucasian SIDS cases and 58 controls and could find no significant association between our Caucasian SIDS cases and controls either for the promoter L allele and the intron 2 12-repeat allele, or for the combined L-12 haplotype as well as the L- or 12-containing genotypes.