Background: Abdominal ultrasonography is a valuable tool for evaluating patients with FUO. A skilled ultrasonographer can examine most abdominal organs and often detect lesions that are not demonstrated by radiography. Aim of the work: The aim of this study is to demonstrate the diagnostic value of a complete standardized ultrasound examination of patients with fever of unknown origin. Patient and methods: We evaluate 60 patients by (ultrasound and colour Doppler) with infection in 32 patients and non-infection in 28 patients. The ultrasound and color Doppler diagnosis was confirmed by histological examination and others images. Results: In this study the US diagnosis were correlated with the final diagnosis based on laboratory examination in 44(73.3%) of the cases, US diagnosis did not correlate with final diagnosis in 16(26.7%) of the cases.  Conclusion: Ultrasound is a valuable non-invasive tool in diagnosis of fever of unknown origin patients.