Background Hypoadiponectinemia has been reported to indicate an increased risk of cardiovascular disease, so the present study investigated the significance of serum adiponectin (APN) levels for predicting clinical outcomes after percutaneous coronary intervention (PCI). Methods and Results The APN levels were evaluated in 184 consecutive patients who underwent PCI. The patients were divided into Group A [the lowest quartile of APN levels (APN ≤4.5 μg/ml), n=46] and Group B [the upper 3 quartiles of APN levels (APN >4.5 μg/ml), n=138]. During a mean follow-up period of 27.3 months, the rate of major adverse cardiac and cerebrovascular events (MACCE: death from any cause, re-infarction, repeat coronary revascularization, hospitalization because of congestive heart failure, and cerebral infarction) was higher in Group A (58.7%) than in Group B (37.0%, p=0.0101). Moreover, when the APN levels were calculated by adjusting for sex, age, body mass index, and triglyceride levels, patients in the lowest quartile of residual APN levels had a higher risk of MACCE (p=0.0405). Multiple logistic analyses showed that hypoadiponectinemia (APN ≤4.5 μg/ml) was independently correlated with MACCE. Kaplan-Meier analysis demonstrated a higher MACCE rate in Group A than in Group B (Log-rank χ²=7.89, p=0.0050). Conclusion The APN level may be helpful for predicting clinical outcomes after PCI. (Circ J 2007; 71: 675 - 680)