The incidence of brain abscess was studied on all cases occurring in residents of Olmsted County, Minn., from 1935 through 1981. Thirty-eight cases (9 cases first diagnosed at autopsy) were identified and followed through the Rochester Olmsted County medical record-linkage system at the Mayo Clinic. The incidence rate was 1.3/100,000 person-years (PY), 1.9 in males and 0.6 in females. Incidence decreased from 2.7 in 1935-44 to 0.9 in 1965-81. Rates were higher in children 5-9 years old (2.4) and after age 60 (2.6 PY). An etiologic agent was identified in 29 cases (76%) with streptococci being the most frequently isolated. Case-fatality ratio was 38% (11/29), stable over time. Concurrent bacterial meningitis was the strongest predictor of death. Neurologic sequelae were observed in 8 (44%) of the 18 surviving patients including epilepsy (5 cases), deafness and motor impairment.