We sought to determine whether differences exist in the factors associated with transient coronary artery (CA) dilation only compared to CA aneurysms after Kawasaki disease (KD). We reviewed all patients with KD assessed and treated at a single tertiary institution from January 1990 to April 2007. Of 1,374 patients (63% men) with KD, 1,108 (81%) had no CA abnormalities; 180 (13%) had CA dilation only, and 86 (6%) had CA aneurysms. The factors associated with any CA abnormality included male gender (odds ratio [OR] 1.8, p <0.001), lower albumin (OR per 1 g/dl, 1.07; p < 0.001), lower hemoglobin (OR per 10 g/dl; 1.02, p = 0.008), diagnosed outside of the 1 to 9-year-age range (OR for <1 year old, 1.5; p = 0.04; OR for >9 years old, 1.9, p = 0.03), longer duration of fever before treatment (OR per day, 1.05, p = 0.002), greater platelet count (OR per 10 x 10(9)/L, 1.14, p = 0.008), and nonresponse to initial intravenous immunoglobulin treatment (OR 2.4, p <0.001). Only age at diagnosis, duration of fever before treatment, greater platelet count, and nonresponse to initial intravenous immunoglobulin discriminated between CA dilation only versus CA aneurysms (c-statistic, 0.80, p <0.001). In conclusion, CA dilation only and CA aneurysms differ only in the total duration of inflammation, as measured by the number of days from fever onset to defervescence.