On the basis of long-term follow up (from 2 to 22 years) of 175 patients with various syndromes of progressive forms of tick-borne encephalitis (TBE), evaluation criteria of TBE progression are systematized. Two basic forms of disease progression are identified: amyotrophic and hyperkinetic, each of them breaking down into a series of leading syndromes. Important for characterizing progressive forms of tick-borne encephalitis (PFTBE) are the time when the disease began to progress and the pattern of progression as well as its stage and severity. PFTBE are correlated with the acute period syndromes. In long-term follow-up, 68% of patients with PFTBE display transformation of clinical forms of the disease, with the formation of the lateral amyotrophic sclerosis syndrome in the overwhelming majority of these patients.