OBJECTIVESEarly-emerging, temperamental differences in fear-related traits may be a heritable vulnerability factor for anxiety disorders. Previous research indicates that the serotonin transporter promoter region polymorphism is a candidate gene for such traits.METHODSAssociations between 5-HTTLPR genotype and indices of fearful child temperament, derived from maternal report and standardized laboratory observations, were examined in a community sample of 95 preschool-aged children.RESULTSChildren with one or more long alleles of the 5-HTTLPR gene were rated as significantly more nervous during standardized laboratory tasks than children who were homozygous for the short alleles. Children homozygous for the short alleles were also rated as significantly shyer, by maternal report, than those with at least one copy of the long allele of the 5-HTTLPR gene.CONCLUSIONSThis study extends the literature linking the short alleles of the serotonin transporter promoter region polymorphism to fear and anxiety-related traits in early childhood and adulthood, and is one of very few studies to examine the molecular genetics of preschoolers' temperament using multiple measures of traits in a normative sample.