In a reveiw of 2,963 patients with signs of infections of the central nervous system in New York State in 1966--1977, arboviruses were found to be the confirmed or presumptive etiologic agents in 60 patients. California encephalitis (CE) virus was the most common (44 patients), followed by Powassan (POW) virus (8), St. Louis encephalitis virus (7), and eastern equine encephalitis (EEE) virus (1). Most patients (47) were children. The incidence of encephalitis was higher in patients with arbovirus findings than in infections with any other of the common neurotropic viruses. The disease was fatal in two patients, one infected with POW virus, the other with EEE virus. Most patients with CE virus infections resided in suburban areas. All POW infections were contracted in six rural counties known for their recreational facilities.