Suicidal ideation is an uncommon but worrisome symptom than can emerge during antidepressant treatment. We have previously described association between treatment emergent suicidal ideation (TESI) and markers in genes encoding the glutamate receptors GRIK2 and GRIA3. The present genome-wide association study was conducted to identify additional genetic markers associated with TESI that may help identify individuals at high-risk who may benefit from closer monitoring, alternative treatments, and/or specialty care. A clinically-representative cohort of outpatients with non-psychotic major depressive disorder enrolled in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial were treated with citalopram under a standard protocol for up to 14 weeks. DNA samples from 90 white participants who developed TESI and a gender and race matched equal number of treated participants who denied any suicidal ideas were genotyped with 109,365 single nucleotide polymorphisms on the Illumina's Human-1 BeadChip. One marker was found to be associated with TESI in this sample at the experiment-wide adjusted p