Tick paralysis is a preventable cause of illness and death that, when diagnosed promptly, requires simple, low-cost intervention (tick removal). We reviewed information on cases of tick paralysis that were reported to the Washington State Department of Health (Seattle) during 1946-1996. Thirty-three cases of tick paralysis were identified, including 2 in children who died. Most of the patients were female (76%), and most cases (82%) occurred in children aged <8 years. Nearly all cases with information on site of probable exposure indicated exposure east of the Cascade Mountains. Onset of illness occurred from March 14 to June 22. Of the 28 patients for whom information regarding hospitalization was available, 54% were hospitalized. Dermacentor andersoni was consistently identified when information on the tick species was reported. This large series of cases of tick paralysis demonstrates the predictable epidemiology of this disease. Improving health care provider awareness of tick paralysis could help limit morbidity and mortality due to this disease.