The retrospective analysis of hematological data on 500 consecutive Saudi patients (342;158F) (mean age 63 +/- 17 yrs) with stroke whose composition was: large infarctions 260 (52%); lacunar infarctions 121 (24.2%), intracerebral hemorrhage 107 (21.2%) and subarachnoid hemorrhage 12 (2.4%), showed that RBC (5.2 +/- 1.9 x 10(12)/L), Hb (143 +/- 21 g/l) and Hct (0.43 +/- 0.07 1/1) values were significantly higher (P < 0.001) in patients with large infarctions as compared to other types of strokes. In both male and female groups of patients, the most likely stroke prone age was 61 to 70 years and interestingly the levels of above three parameters increased or dropped after a certain age. The highest values were in the 61-70 yr age group with men being higher than women (P < 0.001). The overall mortality rate was about 20%, but it was higher in the group of patients with large infarction (63/260; 24.3%). Of these 13 were below the age of 60 years and the remaining 50 aged > 60 included 28 patients (20M;8F) who had Hb > 140 g/l suggesting that Hb > 150 g/L or Hct > 0.44 in men and > 140 g/l or Hct > 0.42 in women is probably a risk factor for having cerebral infarctions and increased mortality. Since this study is neither a cohort nor prospective and was not performed in the acute phase, it was difficult to ascertain if relative polycythemia was a primary event for stroke or was secondary to dehydration in which Saudi hot weather may be a contributory factor.