Using a single dose of local anaesthetics has some disadvantages and provides limited analgesia depending on the pharmacokinetic characteristics of the local anaesthetic used. Nevertheless, the use of continuous perineural infusions allows sustained pain control. Ultrasound-guided interpectoral block followed by the placement of catheters in patients undergoing mastectomies with or without lymph node axillary dissections can result in sufficient pain control. We present a case of a 58-year-old woman undergoing mastectomy and axillary clearance who received ultrasound-guided continuous interpectoral block for postoperative analgesia. After the induction of general anaesthesia, interpectoral ultrasound block was performed and levobupivacaine was administered through a catheter placed between the pectoralis minor and pectoralis major muscles using an ultrasound-guided technique. We used an elastomeric pump containing the 0.125% levobupivacaine anaesthetic solution, with an infusion rate of 5 mL h(-1) for 48 h. Excellent postoperative pain control was observed. Local anaesthetic-and catheter-related side-effects were not observed. The ideal infusion rate for interpectoral block in patients under mastectomy has not been determined. More randomised studies are needed to confirm whether interpectoral techniques are appropriate for routine clinical practice.