Kawasaki disease (KD) is an acute vasculitis predominantly affecting the small arteries of young children. Up to 25% of untreated patients suffer from coronary artery (CA) complications. Early diagnosis and treatment is mandatory in incomplete KD to reduce the risk of coronary involvement. Between 2002 and 2018, 124 patients have been diagnosed suffering from KD at the University Children's Hospital Regensburg (KUNO). We assessed luminal diameters of both CAs normalized as Z-scores by 2D-echocardiography. A total of 94 patients were analyzed. Of them, 31 (33%) were affected by an incomplete form of KD. In 24 children (26%), serial echocardiography was necessary in order to confirm diagnosis. Mean Z-scores for the left main coronary artery (LMCA), right main coronary artery (RMCA), and left anterior descending artery increased significantly between the initial (LMCA 0.79z, RMCA 0.15z, LAD 0.49z) and second (LMCA 1.69z, RMCA 0.99z, LAD 1.69z) examination (p < 0.05). Conclusion:To confirm diagnosis of KD, it might not be necessary to detect dilation or aneurysms. Our observation suggests that patients suspected having KD should be monitored with serial echocardiography in order to detect a possible enlargement of the CA diameters, even if Z-scores are within the normal range. What is Known: center dot Kawasaki disease (KD) is an acute vasculitis predominantly affecting the small arteries of young children. Up to 25% of untreated patients suffer from coronary artery (CA) complications. center dot Due to less classic clinical criteria in patients with incomplete KD, the risk for CA pathology is even higher. What is New: center dot A significant progression of patients' CA Z-scores in serial echocardiographic measurements may be helpful to ensure diagnosis of KD early even if Z-scores are within the normal range. center dot Twenty-seven patients (90%) with incomplete KD could be diagnosed within 10 days of fever, early enough to prevent significantly higher rates of CA aneurysm.