Background: Infantile myofibromatosis is the most common fibrous tumor of infancy. It can involve the skin, muscle, bone, and viscera. This uncommon entity is subdivided into solitary and multicentric forms, with or without visceral involvement., Objective: To describe the imaging characteristics of extracranial myofibromatosis., Materials and Methods: Six infants, aged 1 day-1 week, were evaluated by imaging. All six patients had evaluation of one of the masses by US; four patients had CT evaluation of at least one of the masses; and five patients had evaluation by MRI., Results: The US appearance of the myofibromas included a mass with a purely anechoic center with a thick wall, a mass with a partially anechoic center, and a mass without anechoic components. On enhanced CT, the masses had lower or similar attenuation compared to adjacent muscle, with some masses exhibiting peripheral enhancement. The MR appearance consisted of low signal on T1-weighted imaging. On T2-weighted imaging, two had low signal of the center and the other three had high signal. All masses showed peripheral enhancement after gadolinium administration., Conclusions: Myofibromas have variable appearance on US, with a mass with an anechoic center being the most common feature. On CT, the mass can exhibit peripheral enhancement, calcifications, and erosion of adjacent bone. The MR appearance consisted of low signal on T1-weighted imaging and high or low signal of the center on T2-weighted imaging. All masses showed peripheral enhancement after gadolinium administration.