The aim of this study was to evaluate if the administration of intra-cavitary lidocaine 2% previous to the insertion of LNG-IUS decreases the pain related to the procedure and facilitates the insertion technique of the LNG-IUS in nulliparous patients. This study included 80 nulliparous patients, divided into 2 groups of 40 patients each. One of the groups was allocated to a new technique which first included the visualization of the cervix with a speculum, the passing of a Wallace catheter through the cervix and the intracavitary infusion of 7 cc of lidocaine 2% without epinephrine. The lidocaine was allowed to act for 5 minutes before initiating the insertion. The entire procedure was guided by transabdominal ultrasound. The control group underwent the traditional method of insertion (blind insertion without any local anesthetic). Each patient underwent pain evaluation of the procedure by way of a visual analog scale from 0 to 10, being 10 the maximum pain that they have experienced in their lives and zero no pain. Each medical observer graded the easiness of each technique by way of a verbal analog scale as follows: very easy insertion—easy—difficult- very difficult. The patients which were allocated in the Study Group registered an average pain of 0.75, SD: 0.98, CI of 95% of 0.45–1.05 whereas patients of the Control Group reported an average pain of 4.25, SD:1.84, CI of 3.68–4.82 Evaluation of the easiness of the procedure. The use of a tenaculum was not necessary in 38% of the patients whit the study group and was necessary in 100% of the patients with the traditional method. No infections were presented The use of intracavitary xilocaine previous to the LNG-IUS insertion on nulliparous patients facilitates the procedure and decreases in a significant manner patient's pain and could be a valid alternative insertion method.