Thirty-five patients with suspected chronic osteomyelitis related to an orthopaedic device had 50 99Tcm-HMPAO-labelled leucocyte scans (LS). The scan appearances were compared with the bacteriological or clinical results and gave a sensitivity and specificity of HMPAO-LS of 83 and 100%, respectively. Bacteriological examination is often inaccurate in the diagnosis of osteomyelitis and therefore we assessed the clinical utility of HMPAO-LS. When the clinical, biological and radiological data were clearly suggestive of osteomyelitis (16/50) LS was unhelpful or even misleading when falsely negative (3/16). When the clinical, biological and radiological data were poorly suggestive of osteomyelitis (20/50) or conflicting (14/50) LS was misleading in only one patient (false negative). It is concluded that HMPAO-LS should only be performed to assist in the diagnosis of chronic osteomyelitis when there is no preexisting strong suspicion based on clinical, biological and radiological signs.