Abstract Aim of the work Our study purpose is to evaluate the diagnostic values of high-resolution and power Doppler sonography in early diagnosis of acute osteomyelitis using surgery, aspiration cytology, and follow up as a standard. Patients and methods Twenty seven children (below age 18 years) with symptoms suggesting acute osteomyelitis were included in our series. Plain radiograph was done to each patient followed by gray-scale and power Doppler sonography. Results Twenty five patients (92.6%) were finally diagnosed to have osteomyelitis. Twenty three patients (85.2%) were confirmed by surgery, while two patients (7.4%) were diagnosed by ultrasound guided aspiration of pus. Five sonographic signs could be detected in the disease: (1) deep soft-tissue swelling was the earliest sign which could be seen in the first day of symptoms; (2) periosteal elevation and a thin layer of subperiosteal fluid, which could be progressed to form a subperiosteal abscess (4–6 days). (3) Cortical erosion, which was commonly present in those who had had symptoms for more than a week. (4) Concurrent septic arthritis was evident in 7 patients (25.9%). (5) Increased flow within or around periosteum in power Doppler predicts subsequent subperiosteal abscess formation and failure of antibiotic therapy necessitating surgical intervention with a high sensitivity and positive predictive values reaching 100% Conclusion High resolution and power Doppler sonography were found to be very sensitive and highly specific in diagnosis of acute osteomyelitis in pediatrics with clinical suspicion of the disease and negative or equivocal plain radiographs.