Background Coronary spasm plays an important role in the pathogenesis of ischemic heart disease and it may be associated with low-grade inflammation. Methods and Results Intracoronary injection of acetylcholine was done in 199 patients (99 men, 100 women, mean age, 64.5±11.0 years) with chest pain and normal coronary angiograms. According to the results of the provocation test, the study subjects were divided into 2 groups: the spasm group of 112 patients and the non-spasm group of 87 patients. Clinical data including high-sensitivity C-reactive protein (hs-CRP) and other coronary risk factors were compared between the 2 groups. Serum levels of hs-CRP were significantly higher in the spasm group than in the non-spasm group (median: 1.2 mg/L vs 0.5 mg/L, p<0.005). Multivariate analysis showed that hs-CRP and smoking history were independently associated with coronary spasm with an odds ratio of 2.28 (p=0.027) and 2.25 (p=0.037), respectively, with a hs-CRP value of ≥2 mg/L as cutoff point. Conclusions Minor elevations of the serum hs-CRP level are significantly associated with coronary spasm, suggesting that chronic low-grade inflammation may be involved in the pathogenesis of coronary spasm. (Circ J 2007; 71: 1074 - 1078)