Background and Purpose-Dysglycemia may influence the predictive value of CYP2C19 loss-of-function allele for clinical efficacy of antiplatelet drug, but the role of glycated albumin (GA) remains unclear in patients with stroke on antiplatelet drugs. Methods-The CHANCE trial (Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events) included 2933 patients who had GA levels and CYP2C19 genotyping. Cox proportional hazards model was used to assess the interaction between CYP2C19 loss-of-function allele (*2, *3) carrier status and the effect of antiplatelet therapy based on their GA levels. Results-There was significant interaction between carrier status and antiplatelet therapy regimen on the risk of recurrent stroke (P=0.03) in patients with GA levels of 15.5%, but not in those with GA levels of >15.5% (P=0.48). Only in noncarriers with low GA levels, dual-antiplatelet therapy reduced stroke recurrence (3.5%) compared with those on aspirin alone (14.7%; hazard ratio, 0.23; 95% confidence interval, 0.10-0.49; P<0.001). Similar effects were observed when examined the combined vascular event or ischemic stroke. No significant difference in bleeding was found among groups. Conclusions-In patients with minor stroke or high-risk transient ischemic attack, clopidogrel-aspirin when compared with aspirin alone reduced stroke recurrence only in noncarriers of CYP2C19 loss-of-function allele and normal GA levels.