This study evaluated the relationship between preservation of the intercostobrachial (ICB) nerve and pain sensitivity of the arm, the total time of the surgery, and the number of dissected nodes in patients submitted to axillary lymphadenectomy due to breast cancer. An intervention, prospective, randomized, and double blind study was performed on 85 patients at the State University of Campinas, Brazil, from January 1999 to July 2000. The patients were divided into two groups, according to whether the ICB nerve was preserved or not. The surgeries were performed by the same surgeons, utilizing the same technique. The postoperative evaluations were performed at 2 days, 40 days, and 3 months. The pain sensitivity of the arm was evaluated through a specific questionnaire (subjective evaluation) and through a neurologic examination (objective evaluation). The surgical technique presented a feasibility of 100% and preservation of the ICB nerve was related to a significant decrease in the pain sensitivity of the arm, both in the subjective and objective evaluations. After 3 months, in the subjective evaluation, 61% of the patients were asymptomatic in the ICB nerve preservation group, with 28.6% in the nerve section group (p<0.01). In the objective evaluation, 53.7% of the patients presented normal neurologic examination in the ICB nerve preservation group, with 16.7% in the nerve section group (p<0.01). No significant difference was observed in the total time of the surgery (p=0.76) and the number of dissected nodes between the two groups (p=0.59). Local relapse was not observed in any group after 36 months of follow-up. These data support that preservation of the ICB nerve is feasible and leads to a significant decrease in the alteration of pain sensitivity of the arm, without interfering with the total time of the surgery, the number of dissected nodes, and local relapse rate.