Ultrasonography is an important modality for evaluation of musculoskeletal infections in children because it is rapid, nonionising and very sensitive for (infectious) fluid collections and joint effusions. Moreover, the images are not degraded by metallic or motion artefacts (as with CT and MRI) and finally, ultrasonography offers the possibility of fine-needle aspiration to confirm the infectious nature of a fluid collection without unnecessary contamination of adjacent anatomical compartments. Ultrasonography should be combined with radiography because both imaging techniques are complimentary. The purpose of this article is to emphasise the role of ultrasonography in the diagnosis of various diseases in childhood, including cellulitis, subcutaneous abscess, necrotizing fasciitis, pyomyositis, infectious bursitis and arthritis, osteomyelitis, foreign bodies and infectious lymphadenitis. Along with conventional radiography, ultrasonography is a very valuable modality for early diagnosis and follow-up of musculoskeletal infections in children.