Imaging modality has become increasingly important in hospital setting especially in cases of unknown site of infection/pyrexia of unknown origin (PUO) and osteomyelitis (OM). In recent years, nuclear imaging has been used and is known to deliver prompt and precise diagnoses of numerous infectious diseases. The purpose of the study is to detect and localise the site of infection using Tc99m-besilesomab and to assess the added contributions of single photon emission computed tomography/computed tomography (SPECT/CT) over planar scan in patients with PUO and OM. Methods: Tc99m-besilesomab with SPECT/CT were prospectively performed in 23 patients (eight males, 15 females) with suspected infection. True findings were diagnosed by both cold and hot spot in the scan with reference to positive blood or tissue cultures, or other additional imaging. Results: Tc99m-besilesomab managed to detect presence of infection with high sensitivity of 87.5% and specificity of 71.4%. Interobserver variability agreement that was obtained between the presence of infection and the ability of Tc99m-besilesomab imaging to detect it was significant (p