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Effective in treatment-resistant depression (TRD), repetitive transcranial magnetic stimulation (rTMS) presents a remission rate between 30% and 40%. Although genetics could be one potential source of inter-individual variability in rTMS responsiveness, few studies have sought to identify possible genetic basis of rTMS response [1,2]. Therefore, we used an extreme-phenotype design in which we compared genome-wide allelic variation between rigorously defined rTMS responders and non-responders.A total of 99 TRD patients provided informed consent and this study was approved by the Human Research and Ethics Committee of the Alfred Hospital. All were submitted to a rTMS protocol and completed at least 18 sessions of 10 Hz at left dorsolateral prefrontal cortex (DLPFC). Clinical outcomes (responder or non-responder) were determined based on scores on the Montgomery Asberg Depression Rating Scale (MADRS).We used the extreme-phenotype design. Patients were separated into two groups, responders -patients with at least 60% reduction on the MADRS scale (n ¼ 29) and non-responders -patients with 10% or less reduction on the MADRS scale (n ¼ 19). We used this criteria considering that extreme scoring patients (<10 >60) may present more representative genetic results, improving power to detect phenotype-genotype associations [3,4].Genotyping was performed using the Infinium PsychArray-24 BeadChip (Illumina, Inc., San Diego, CA, USA) and analyzed with PLINK 1.9. We performed quality control to remove individuals or markers with high error rates. Data quality control parameters were: call rate (GENO) > 90%, maximum individual missingness rate (MIND) < 10%, minor allele frequency (MAF) > 5% and Hardy-Weinberg equilibrium (HWE) p-value > 10e6. We performed standard association analysis to compare allele frequency in both groups with a 95% CI. After identifying the significant SNPs and genes a functional enrichment analysis using STRING and Cytoscape databases was performed.