The authors report six children (five girls, one boy) aged 11 to 13 years, of whom four had clinically definite multiple sclerosis (MS) and two had laboratory-supported definite MS. All had brain white matter abnormalities indicative of MS. In three cases, positive findings on the first MRI contributed significantly to their early diagnosis. Follow-up MRI studies over an average period of five months detected morphological changes in three of the children, although there was no concomitant clinical evidence. This raises the question of whether changes in clinically 'silent' lesions on follow-up MRI are antecedents of the essential MS criterion of dissemination over time, which could lead to earlier diagnosis of childhood MS. With cranial computerized tomography (CT) during the first clinical attack, a large focus with a lamellar structure mimicked a brain tumour in two patients. As CT also misses additional small lesions, it should no longer be used as the primary diagnostic method.