Polymorphisms at genes encoding proteins involved in the pathogenesis of psoriasis (Psor) or in the mechanism of action of biological drugs could influence the treatment response. Because the interleukin (IL)-17 family has a central role in the pathogenesis of Psor, we hypothesized that IL17RA variants could influence the response to anti-TNF drugs among Psor patients. To address this issue we performed a cross-sectional study of Psor patients who received the biological treatments for the first time, with a follow-up of at least 6 months. All of the patients were Caucasian, older than 18 years old, with chronic plaque Psor, and had completed at least 24 weeks of anti-TNF therapy (adalimumab, etanercept or infliximab). The treatment response to anti-TNF agents was evaluated according to the achievement of PASI50 and PASI75 at weeks 12 and 24. Those who achieved PASI75 at week 24 were considered good responders. All patients were genotyped for the selected single-nucleotide polymorphisms (SNPs) at IL17RA gene. A total of 238 patients were included (57% male, mean age 46 years). One hundred and five patients received adalimumab, 91 patients etanercept and 42 infliximab. The rs4819554 promoter SNP allele A was significantly more common among responders at weeks 12 (P=0.01) and 24 (P=0.04). We found a higher frequency of AA versus AG+GG among responders, but the difference was only significant at week 12 (P=0.03, odd ratio=1.86, 95% confidence of interval=1.05-3.27). Thus, in the study population, the SNP rs4819554 in the promoter region of IL17RA significantly influences the response to anti-TNF drugs at week 12.