Objective:The aim of this study was to compare the pain perception and side effects during and after endovenous laser ablation with a 1470 nm diode laser using cold or room temperature tumescence anesthesia. Methods:One hundred and one patients were randomly assigned in two groups. Group A received room temperature (+24?) and Group B received cold (+4?) tumescence fluid, which was used for local anesthesia in the track of great saphenous vein. A visual analog score was recorded immediately after the procedure. Patients were asked to register pain scores and the amount of pain medication consumed during the week. Results:There was no significant difference concerning gender, age, Clinical Etiological Anatomical Pathological Classification, body mass index, or diameter of the treated vein. In Group A, the mean linear endovenous energy density was 59.5 J/cm and in Group B, it was 60.4 J/cm. The average visual analog score after the endovenous laser ablation procedure in Group A was 5 and in Group B was 2. Third day after the procedure, the average visual analog score in Group A was 3 and in Group B was 1. Patients in Group B needed significantly less analgesics compared with patients in Group A (p<0.05). The most frequent side effects in both groups were ecchymosis, induration, and minor paraesthesia, all of which were more common in Group A (p<0.001). Conclusions:To date, most published endovenous laser ablation series describe the use of room temperature tumescence fluid infiltration of the perivenous stroma for tumescent analgesia and protection against thermal injury to the nearby structures. We describe an alternative technique using cold tumescence fluid infiltration, which is equally effective as, but safer than, room temperature tumescence fluid infiltration, and which yields better visual analog scores.