In 1976 blood samples from 748 patients were tested for complement fixation antibodies against the virus of tickborne encephalitis. Of these, 38 had antibodies in a serum dilution of 1:8, 18 also in a dilution of 1:32 or higher. Clinical symptoms, laboratory results, time and place of illness are presented in more detailed analysis for 14 cases. From these data, it appears than tick-borne encephalitis is more wide-spread in southeastern Bavaria than has been previously supposed. In most of the cases, tick-borne encephalitis was not suspected because the patients generally did not have a bi-pattern of illness, only 6 of the 14 had a definite history of a tick-bite, and, moreover, atypical features frequently occurred in addition to CNS symptoms. The number of juvenile patients (4 out of 14) was also unexpected. Attention is drawn to the present situation with regard to passive and active immunization.