Background: Studies on focal cerebral blood flow and brain behavior during the interphase of transient ischemic attack (TIA) are still in the preliminary stage. Single-photon emission computed tomography (SPECT) and positive-photo emission tomography (PET) have been used in some developed countries to observe the brain blood flow and behavior and revealed cerebral hypoperfusion and focal neurological dysfunction during the interphase of TIAs. But their correlation is poorly known. Objective: To explore basis for effective intervention and treatment by observing the focal cerebral blood flow and corresponding brain behavior during the interphase of TIAs. Design: Cross-sectional observation. Setting and participants: Forty-one TIA inpatients were confirmed between June 2001 and July 2002 at the Department of Neurology, Xuanwu Hospital, Capital University of Medical Sciences. Forty-five people without neurological diseases, which were confirmed by from routine physical examinations, were enrolled as controls. Patients with diabetes or severe heart, liver and kidney diseases were excluded. Interventions: Patients underwent SPECT, CTPI, and PET examinations within 1-7 days following the last attack of TIA. Main outcome measures: Focal cerebral blood flow and brain function by SPECT, CTPI, and PET examinations. Results: Radiosparsity or defect rate or both was 95% (39/41) by SPECT examination in 41 patients, and perfusional dysfunction rate was 63% (26/41) by CTPI, indicating that more than half of patients with TIA had focal cerebral blood flow abnormality at corresponding regions during the interphase. Subjects who had normal blood flow but with radiosparsity or defect or both were considered due to the reduced regional cerebral function. Glucose metabolism decrement was also found in focal brain by PET at the same time. Conclusion: Although no clinical signs and symptoms can be found in patients during the interphase of TIAs, neuronal function is not completely restored, and some patients still have cerebral hypoperfusion. Even those whose blood flow return to normal still have focal functional defects. Therefore, treatment of TIA shall not focus only on improving blood flow but also on protecting brain function, which is important for preventing recurrent TIA and brain stroke.