Congenital-infantile, fibrosarcoma is a rare tumour presenting at birth or in the neonatal period. Few such tumours have been reported, and imaging details in particular are scant. The authors describe two neonates with congenital-infantile fibrosarcoma, the first case involving the right thigh and extending into the pelvis, and the second involving the calf and the ankle. In both cases magnetic resonance imaging (MRI) demonstrated well-demarcated, low-signal-intensity soft-tissue masses with t1-weighting and inhomogeneous, high-signal-intensity masses with T2-weighting. MRI was superior to other imaging modalities in the assessment of soft-tissue involvement and proved especially useful in planning therapy and monitoring chemotherapeutic response.