Intravenous propacetamol has been shown to be effective for postoperative pain control. However, the recommendations regarding propacetamol doses for pain control are vague. The present study was performed to compare the efficacy and safety of propacetamol at a dose of 1 g or 2 g. After breast-conserving surgery, patients received 1 g or 2 g intravenous propacetamol. Treatment efficacy for pain control was assessed using a 100 mm visual analog scale at 15, 30, 45, and 60 minutes and 4 hours after surgery, and global evaluation was assessed by a 4-point categorical scale at the end of the 4-hour study period.