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To compare the circadian variation of blood pressure (BP) between patients with intra-cerebral haemorrhage (ICH) and with cerebral infarction (CI), around-the-clock BP measurements were obtained from 89 hypertensive patients with ICH, from 63 patients with CI and from 16 normotensive volunteers. The single and population-mean cosinor yielded individual and group estimates of the MESOR (Midline Estimating Statistic Of Rhythm, a rhythm-adjusted mean value), circadian double amplitude and acrophase (measures of extent and timing of predictable daily change). Comparison shows that without any difference in BP MESOR, the circadian amplitude of systolic (S) BP was larger in ICH than CI patients (P<0.001), and both groups differed from the healthy volunteers in BP MESOR and pulse pressure (P<0.001) and in the circadian amplitude of SBP (P<0.005). The smaller population circadian amplitude of diastolic (D) BP of the ICH group (P=0.042) is likely related to a larger scatter of individual circadian acrophases in this group as compared with that in the other two groups, an inference supported by a smaller day-night ratio of DBP for ICH vs CI patients (P=0.007). Heart rate (HR) variability, gauged by the standard deviation (SD), was decreased in both patient groups as compared with that in healthy controls, more so among ICH than CI patients (P=0.025). Thus, patients with ICH had a higher incidence of abnormal circadian characteristics of BP than patients with CI, the major differences relating to a larger circadian amplitude of SBP, a smaller HR-SD, and a larger incidence of odd circadian acrophases of DBP.