Hypertension (HT) is the most attributable and modifiable risk factor for spontaneous intracerebral hemorrhage (SICH). However, epidemiological data on blood pressure (BP) control before SICH and its relationship to patient lifestyles are lacking. This study prospectively enrolled patients with acute SICH from six stroke centers in Tochigi, Japan. BP control and patient lifestyles were investigated using a questionnaire conducted on patients and their families. A total of 365 patients were analyzed, 270 (74.0%) of whom had HT and 198 (54.2%) untreated HT. The prevalence of untreated HT was much higher in younger patients and decreased with age (79.0%, 71.8%, 62.2%, 44.8%, and 31.0% in those aged <
50, 50-59, 60-69, 70-79, and ≥80 years, respectively). Patients with untreated HT were significantly less likely have a family doctor and attended fewer annual health checkups than did those with treated or no HT. Untreated HT with awareness was much higher in younger and middle-age men than in women, whereas untreated HT without awareness was much higher in younger women than in men. Among patients who received antihypertensives, the prevalence of well-controlled HT was also very low, especially in younger patients (20.0% and 23.5% in those aged <
50, and 50-59 years, respectively). In-hospital mortality was much higher in younger patients (age <
70 years) with untreated than with treated or no HT. Untreated and uncontrolled HT were highly detected and seemed to be important targets for the primary prevention of Japanese SICH. Different strategies to improve BP control are warranted for each generation and sex.