Purpose: This study investigated the epidemiology of Kawasaki disease (KD) in infants ${leq}3$-month-old. Methods: To study the epidemiology of KD in Korea, data for 27,851 KD patients were collected on a 3-year basis between 2000 and 2008 in a retrospective survey. From this, data for 609 KD patients ${leq}3$-month-old were analyzed and compared with the data for KD patients >3-month-old. Results: The 609 KD patients ${leq}3$-month-old (385 males and 224 females) constituted 2.2% of the KD patients. They included 25 infants <1-month-old, 198 infants ${leq}1$- to 2-month-old, and 386 infants >2- and 3-months-old. The ratio of males to females was 1.72:1. The incidence of coronary artery (CA) dilatation (19.9% vs. 18.7%) and CA aneurysms (3.4% vs. 2.6%) detected by echocardiography did not differ significantly between patients with KD younger and older than 3-month-old. Conclusion: Compared with the data for the KD patients >3-month-old, the data for the 609 patients ${leq}3$-month-old did not show a significantly higher incidence of CA dilatation or CA aneurysms.