The number of ambulatory surgical procedures is growing and local anesthesia represents the technique of choice for outpatients undergoing minor surgery. The aim of this study was to verify whether differences exist in postoperative pain relief using equipotent doses of two long-acting local anesthetics, ropivacaine and levobupivacaine, in patients who underwent minor breast surgery. A series of 86 consecutive women (median age=55, range=39-75 years) with small (<2 cm in size) breast masses requiring surgical excision were prospectively enrolled in the study. Patients were randomly selected to receive 7.5 mg/ml ropivacaine (group A, 42 patients) or 5 mg/ml levobupivacaine (group B, 44 patient). For post-surgical measurement of pain intensity a visual analog scale (VAS) was used. The age of the patients (56.4±9.6 vs. 56.7±9.5 years; p=0.88) and operative time (38.4±4.3 vs. 39.8±5.0 min; p=0.16), did not differ significantly between the groups (A vs. B). Transient adverse effects were observed in 5 (11.9%) and 4 (9.1%) patients (p=0.49) of groups A and B, respectively. The pain VAS four (t4) and 24 (t24) hours from the end of surgery was significantly (p<0.05) different between the groups, but an inversion of pain relief efficacy and a crossing point of the two pain-time lines at the sixth hour was observed. In conclusion, ropivacaine results in more effective pain relief at time t4, while levobupivacaine should be the drug of choice when long-term postoperative analgesia is required.