From 1975–1979, the incidence of primary intracerebral hemorrhage (PIH) increased in Rochester, MN, when compared with a previously decreasing incidence. Judging from patients with PIH who were alert at diagnosis, we estimated that 24% of the hemorrhages in earlier years had been mislabeled as infarction. The 30-day survival rate increased from 8% in 1945–1974 to 44% in 1975–1979. The incidence rate was about 45% higher in patients receiving anticoagulant treatment than in those who did not. The increased incidence rate and improved survivorship were attributed to more frequent identification of small PIH by CT.