The aims of this study were to determine the incidence of hypertrophic pulmonary osteoarthropathy (HPO) in nasopharyngeal carcinoma (NPC) and assess its clinical significance. Altogether, 407 NPC patients were reviewed retrospectively. HPO was identified by 99Tcm-methylene diphosphonate bone scans and related clinical and radiographic evidence. Pulmonary metastases, bony metastases and titre of anti-Epstein Barr virus (EBV) immunoglobulin were assessed in patients with and without HPO. The patients had a mean (+/- S.D.) age of 50.4 +/- 12.4 (range 17-73) years. HPO was found in 27 of the 407 (6.6%) NPC patients, among whom 13 (48%) had pulmonary metastases. HPO preceded lung metastases by 7-22 months (14.4 +/- 6 months) in 7 (52%) patients. Six patients had overt lung metastases at the time of the bone scan. No significant difference was found in anti-EBV immunoglobulins between the patients with or without HPO, nor in the incidence of bony metastases between these two groups of patients. HPO should be regarded as an early sign of pulmonary metastases.