The HLA antigens B7 and Dw2 occurred at elevated frequencies in 105 multiple sclerosis (MS) patients (49 and 47%, respectively), compared to healthy controls (29 and 30%), especially in MS patients with oligoclonal CSF-IgG (51 and 50%), in cases with CSF-IgG index values above 1.5 (64 and 64%), and in those with the most malignant course of the disease (47 and 59%). Normal or only slightly elevated frequencies of B7 and Dw2 were found in MS patients without oligoclonal CSF IgG (35 and 29%), normal CSF-IgG index (43 and 39%), and the most benign course (42 and 37%). No correlation was found between the HLA type and measles virus antibody titers in serum or a measles virus antibody response within the CNS.