Objective: Epidural analgesia is the gold standard for post-thoracotomy pain relief but is contraindicated in certain patients. An alternative is paravertebral block. We investigated whether ropivacaine, administered through a paravertebral catheter placed by the surgeon, reduced postoperative pain. Methods: In a randomized double-blind study, adult patients with a paravertebral catheter placed by the thoracic surgeon after thoracotomy were randomly assigned to receive through this catheter, either a 0.1 ml kg−1 bolus of 0.5% ropivacaine, followed by a continuous infusion of 0.1 ml kg−1 h−1 for 48 h, or saline at the same scheme of administration. Patients also benefited from patient-controlled analgesia with intravenous morphine (bolus 1 mg, lockout time 7 min), paracetamol, and nefopam. The primary endpoint was pain intensity on a visual analog scale at rest and on coughing. Secondary endpoints were total morphine consumption and side effects during the first 48 postoperative hours. Surgeons, anesthesiologists, and all the nurses and caring staff involved in this study were blinded. Solutions of saline and ropivacaine were prepared identically by the central pharmacy, without any possible identification of the product. Results: Forty-seven patients with contraindications to epidural anesthesia were included. There were no significant differences between the groups receiving ropivacaine and saline in terms of pain severity at rest and on coughing, mean postoperative morphine consumption (45.7 mg for ropivacaine, 43.2 mg in controls), and incidence of morphine-related side effects (nausea and vomiting, urinary retention, pruritus, respiratory rate, and sedation). Conclusions: Paravertebral block using a catheter placed by the thoracic surgeon was ineffective on postoperative pain after thoracotomy and did not confirm the analgesic effect that has been observed after percutaneous catheter placement. A direct comparison of these two placement methods is required.