A promoter polymorphism in the serotonin transporter gene has been widely studied in neuropsychiatry. We genotyped the 5HTTLPRrs25531 triallelic polymorphism in 728 schizophrenia cases from the CATIE study and 724 control subjects. In a logistic regression with casecontrol status as dependent variable and 7 ancestryinformative principal components as covariates, the effect of 5HTTLPRrs25531 composite genotype was not significant odds ratio 1.008, 95 CI 0.868–1.172, P 0.91. In cases only, 5HTTLPRrs25531 was not associated with neurocognition summary neurocognitive index P 0.21, working memory P 0.32 or symptomatology PANSS positive P 0.67 and negative symptoms P 0.46. We were unable to identify association of the triallelic 5HTTLPR with schizophrenia, neurocognition, or core psychotic symptoms even at levels of significance unadjusted for multiple comparisons. © 2010 WileyLiss, Inc.