Background: Kawasaki disease (KD) is an acute systemic vasculitis that occurs in children and may lead to cardiovascular morbidity and mortality. Progressive coronary dilatation for at least 2 months is associated with worse late coronary outcomes in patients with KD having medium or giant aneurysms. However, the risk factors and occurrence of progressive coronary dilatation in patients with KD but without medium or giant aneurysms have been insufficiently explored. Methods: We retrospectively enrolled 169 patients with KD from a tertiary medical center in Taiwan during [2009][2010][2011][2012][2013]. Medical records of all patients were reviewed. Echocardiography was performed during the acute KD phase and at 3-4 weeks, 6-8 weeks, 6 months, and 12 months after KD onset. Progressive coronary dilatation was defined as the progressive enlargement of coronary arteries on three consecutive echocardiograms. Logistic regression analysis was conducted to evaluate the potential risk factors for coronary aneurysms and progressive coronary dilatation. Results: Of a total of 169 patients with KD, 31 (18.3%) had maximal coronary Z-scores of ≥ + 2.5 during the acute KD phase, 16 (9.5%; male/female: 9/7) had coronary aneurysms at 1 month after KD onset, and 5 (3.0%) satisfied the definition of progressive coronary dilatation. Multivariate logistic regression analysis revealed that an initial maximal coronary Z-score of ≥ + 2.5 [odds ratio (OR): 5.24, 95% confidence interval (CI): 1.31-21.3, P = 0.020] and hypoalbuminemia (OR: 4.83, 95% CI: 1.11-20.9, P = 0.035) were independent risk factors for coronary aneurysms and were significantly associated with progressive coronary dilatation. However, the association between intravenous immunoglobulin unresponsiveness and the development of coronary aneurysms at 1 month after KD onset didn't reach the level of significance (P = 0.058). Conclusions: In the present study, 3% (5/169) of patients with KD had progressive coronary dilatation, which was associated with persistent coronary aneurysms at 1 year after KD onset. Initial coronary dilatation and hypoalbuminemia were independently associated with the occurrence of progressive coronary dilatation. Therefore, such patients may require intensive cardiac monitoring and adjuvant therapies apart from immunoglobulin therapies.