Twenty-five children and young adults with myelin disorders were studied to determine how magnetic resonance (MR) findings correlated with the clinical severity of their disease. The MR images were evaluated using both subjective and objective criteria and graded for extent of white matter involvement. Patients were also graded for severity of their neurological and psychological impairment. The assessment of MR severity of white matter involvement using subjective and objective methods showed moderate to good correlation (r2 = 0.473). There was poor correlation between clinical severity of disease and extent of MR involvement for the overall group of children, however (subjective r2 = 0.038, objective r2 = 0.072). Moderate correlation was seen when clinical severity and MR subjective assessment were compared for the specific diseases metachromatic leukodystrophy and subacute sclerosing panencephalitis.