Background: The effects of age and hematocrit on transcranial Doppler (TCD) velocities have not been evaluated in a large patient group with recent ischemic stroke. Aim: This study assessed the effects of age and hematocrit on TCD measurements in patients with recent ischemic stroke compared to patients with non-vascular diseases. Settings and Design: University Hospital, retrospective study. Materials and Methods: TCD records and data files of 862 consecutive patients (mean age, 57 +/- 16 years) with various neurological diagnoses were reviewed retrospectively. The peak systolic, end diastolic and mean flow velocities (FV), systolic/diastolic ratios and pulsatility indices (PI) in the middle cerebral arteries were averaged and the effect of age and hematocrit values on these TCD values was studied. Independent samples t test, Pearson's coefficients of correlation, and linear regression test were used for statistical analysis. Results: Among 862 patients, 413 were women (mean age, 53 +/- 17 years) and 449 were men (mean age, 60 +/- 13 years). Peak systolic and mean FV were higher and hematocrit concentration was lower in women compared to men (P < 0.001). The relation of TCD velocities with age and hematocrit was more remarkable in the group of patients with non-vascular neurological disorders. PI values demonstrated a significant correlation to age (r=+0.47) (P < 0.001), but did not change significantly with hematocrit level. Conclusions: It should be remembered that blood FV measured by TCD may be significantly affected by age and hematocrit level. However, there seems to be no significant association between TCD velocities and hematocrit in patients with a recent ischemic stroke.