Twenty-five patients with definite or probable Rocky Mountain spotted fever (RMSF) who were hospitalized for > or = 2 weeks were identified from our database of 105 patients. Follow-up information was collected for 20 patients, per telephone and/or medical records. The remaining five patients were lost to follow-up or died. Nine patients had > or = 1 long-term sequelae (defined as complications related to an original acute infection with Rickettsia rickettsii that persisted for > or = 1 year following hospital discharge). The ages of patients with sequelae ranged from 2 to 74 years (mean and median, 38 years); duration of follow-up ranged from 1 to 18 years (mean, 11 years). The mean lengths of hospitalization for patients with and without long-term sequelae were 47 days and 20 days, respectively (P < .05). Long-term neurological sequelae included paraparesis; hearing loss; peripheral neuropathy; bladder and bowel incontinence; cerebellar, vestibular, and motor dysfunction; and language disorders. Nonneurological sequelae consisted of disability from limb amputation and scrotal pain following cutaneous necrosis. These data suggest that significant long-term morbidity is common in patients with severe illness due to RMSF.