Previous methods for determining limb length during hip arthroplasty have depended on physical examination and direct measurement techniques. A radiographic technique for assessing limb length intraoperatively with a single anteroposterior (AP) pelvis radiograph was studied in 46 consecutive hip arthroplasties in 41 patients (five with bilateral arthroplasties). Of the 41 patients, 97.6% had either an average postoperative limb length discrepancy of 2.9 mm (-1 mm to +7 mm), or the limb was lengthened no more than 7 mm. This radiographic method has led to one of the most successful results reported in the literature with regard to minimizing significant limb length discrepancy or limb lengthening (maximum of 7 mm) following total hip arthroplasty. The single AP radiograph made intraoperatively with the trial implant in place is a valuable aid in determining limb length in total hip arthroplasty. (Hip International 2005; 15: 199-205).