The glutamate transporter gene SLC1A1 has been shown to have an association with obsessive-compulsive disorder (OCD), and serotonin reuptake inhibitor (SRI) treatment response. One polymorphism (rs3056) in SLC1A1 has been associated with altered brain volumes in OCD. We investigated the association of this polymorphism with OCD and its relationship with various clinical parameters, including age of onset, disease severity, insight, factor analyzed symptom dimensions of OCD, and SRI treatment response. Three hundred seventy seven OCD patients (DSM-IV) aged between 18 to 60 years were recruited from a specialty OCD clinic. To study the association with SRI treatment response, we analyzed full responders (≥35% reduction in the Yale Brown Obsessive Compulsive Scale [YBOCS] and the Clinical Global Impression-Improvement [CGI-I] score of 1 or 2) to any SRI (n = 187) and nonresponders (<25% reduction in the YBOCS and the CGI-I score >4) to adequate trials of at least two SRIs for a duration of 12 weeks (n = 91). Healthy controls (n = 333) were recruited and evaluated using the Mini-International Neuropsychiatric Interview-Plus (MINI-Plus). All subjects were from southern India, and were genotyped for the SLC1A1 polymorphism (rs3056). Genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium. Case-control association analysis revealed that the "GG" genotype was significantly more frequent in OCD cases than the controls (p = .04). No association was found with the age of onset, symptom severity, insight, and symptom dimensions. No significant association was found between genotype/allele frequencies with treatment response. To conclude, although there was a significant association between the SLC1A1 rs3056 polymorphism and OCD, there were no significant associations with other clinical parameters or treatment response. (PsycInfo Database Record (c) 2020 APA, all rights reserved).