Breast augmentation surgery can cause important postoperative pain, especially when bilateral subpectoral implants are used. The investigators hypothesized that a technique of regional analgesia, the pectoral nerve block type I (or "PECS I block") would reduce pain within the first twenty-four hours and, in turn, morphine consumption and associated side effects. This is a randomized, controlled, double-blind study which compares intra and postoperative analgesia with or without PECS I block in breast surgery.

Inclusion Criteria:

• Every female who will benefit of a bilateral subpectoral breast augmentation
• Age more than 18 years
• Social insured

Exclusion Criteria:

• refusal of the patient
• Age less than 18 years
• Inability to consent
• History of thoracic surgery or breast implants
• Pregnancy
• Inability to use a patient controlled analgesia
• Contraindication of the use of opioids or local anesthetics
• Pathology of hemostasis, infection
• Can not use a PCA
• Patients under long-term opioids (WHO pain ladder 2 and 3)
• Patient presenting neuropathic pain during the preoperative period (score greater than or equal to 4 to the DN4 questionnaire, or taking anti-epileptic or antidepressant treatments for neuropathic pain)