The aim of the study was to evaluate whether the surgical treatment reserved for the ilioinguinal, iliohypogastric and genital branches of the genitofemoral nerves, during open hernia mesh repair, is effective in reducing chronic post-operative pain. A multicentre prospective study involving 11 Italian Institutions led to the recruitment of 973 cases of hernioplasty. All surgeons were asked to report whether or not each nerve had been identified and preserved or divided. The main endpoint of the study was the evaluation of moderate-severe chronic pain at 6 months and 1 year. Overall, presence of groin pain at 6 months and 1 year follow-up was 9.7% and 4.1%, respectively. Pain was mild in 7.9% and moderate-to-severe in 2.1% at 6 months, and mild in 3.6% and moderate-to-severe in 0.5% at 1 year. Univariate and multivariate analysis showed that lack of identification of nerves is significantly correlated with presence of chronic pain, the risk of developing inguinal pain increasing with the number of nerves not detected. Likewise, division of nerves was clearly correlated with presence of chronic pain. The present findings indicate that identification and preservation of nerves during open inguinal hernia repair reduce chronic incapacitating groin pain.