Objectives: During visual stimulation, the elevated metabolism rate will coupl e with increase of blood flow velocity(BFV) in posterior cerebral artery(PCA). T his study with TCD was aimed to investigate whether the coupling might change ac cording to the different vasoneuronal conditions. Methods: Ninety-nine voluntee r s including 24 hypertension(HT) patients and 2 patients suffering from both HT a nd diabetes mellitus(DM) were enrolled in this trial. BFV and pulse indexes(PI) in P2 segments of PCA on both sides were monitored during visual stimulation. Re sults: In all subjects, Mean BFV increased and PI went down in response to visua l stimulation. The percentages of changes (ΔV and ΔP) of both mean BFV and PI we re larger in young group(<55 years old) than in old one(≥55 years old). There w a s significant positive correlation between ΔV and ΔP. Multivariated re gression a nalysis did not show HT and DM, but age related to ΔV(ΔP). We did not find signi ficant difference of ΔV(ΔP) between left and right sides. Conclusions: Blood flo w velocity in PCA P2 segment increased due to decreased cerebrovascular resistan ce during visual stimulation and the response weakened with aging of the patient . Objectives: During visual stimulation, the elevated metabolism rate will coupl e with increase of blood flow velocity (BFV) in posterior cerebral artery (PCA). T his study with TCD was aimed to investigate whether the coupling might change ac cording to the different vasoneuronal Conditions. Methods: Ninety-nine voluntee rs including 24 hypertension (HT) patients and 2 patients suffering from both HT a nd diabetes mellitus (DM) were enrolled in this trial. BFV and pulse indexes (PI) in P2 segments of PCA on both The sults were monitored during visual stimulation. Re sults: In all subjects, Mean BFV increased and PI went down in response to visua l stimulation. The percentages of changes (ΔV and ΔP) of both mean BFV and PI we re larger in young group ( <55 years old) than in old one (> 55 years old). There was a significant positive correlation between ΔV and ΔP. Multivariated re gression a nalysis did not show HT and DM, but age related to ΔV (ΔP). We did not find signi ficant difference of ΔV (ΔP) between left and right sides. Conclusions: Blood flo w velocity in PCA P2 segment increased due to decreased cerebrovascular resistan ce during visual stimulation and the response weakened with aging of the patient.