Background Elevated C-reactive protein (CRP) is associated with adverse outcomes in non-ST-segment elevation acute coronary syndromes (NSTE-ACS); however, the prognostic significance of serum amyloid A (SAA), also an important inflammatory marker, remains unclear. Methods and Results The ability of SAA, in combination with CRP, to predict clinical outcomes was evaluated in 277 patients with NSTE-ACS. Patients were classified according to the presence or absence of elevated SAA (>0.8 mg/dl) and elevated high-sensitivity CRP (>0.200 mg/dl) on admission: group 1, both SAA and CRP normal (n=133); group 2, SAA normal, but CRP elevated (n=30); group 3, SAA elevated, but CRP normal (n=28); and group 4, both SAA and CRP elevated (n=86). In groups 1, 2, 3, and 4, the rates of combined endpoints including death, (re)infarction, or urgent target-vessel revascularization at 30 days were 8%, 3%, 25%, and 23%, respectively (p=0.002). Multivariate analysis showed that as compared with group 1, the odds ratios for combined endpoints in groups 2, 3, and 4 were 0.50 (p=0.30), 1.95 (p=0.038), and 1.86 (p=0.044), respectively. Conclusions Regardless of the level of CRP, elevated SAA is associated with adverse 30-day outcomes in patients with NSTE-ACS, so SAA is a better predictor of clinical outcome than CRP in these patients. (Circ J 2007; 71: 186 - 190)