The outcomes of diseases caused by Inkoo and Tahyna viruses are favorable. No lethal cases were observed. Altogether 16.7% of convalescents after the febrile form of the disease and 30.7% convalescents after the neuroinfections form develop 1 to 2.5 years after the disease (follow-up period) asthenoneurologic disturbances and microfocal neurologic symptoms. Blood sera of 118 patients with chronic neurologic diseases were tested in the neutralization test with Inkoo and Tahyna viruses. Summary antibodies to Inkoo and Tahyna viruses were detected in 26 (70.3%) of 37 examined patients with disseminated encephalomyelitis. The findings point to necessity of further study of the possible role of California encephalitis group viruses in the etiology of chronic neuroviral infections.