Fifty-five patients with 60 suspected infections of bones or joints were studied with 99mTc-hexamethylpropyleneaminooxine- (HMPAO-) labelled leucocytes and 99mTc-labelled antigranulocyte antibodies, in part supplemented with 99mTc-labelled nanocolloid. The findings using the different procedures were in good agreement. Apart from in vertebral lesions, a negative scan--even if the radionuclide bone scan is positive--excludes an infection with high probability (sensitivity 94%). The low specificity (57%) is due to positive imaging of various non-infected lesions. Spondylitis usually shows as non-specific cold lesions. A subtraction technique with computer assisted analysis of HMPAO and nanocolloid scans provides a more precise diagnosis of this condition.