In clinical practice, the most important points for accurately diagnosing neonatal infections are: immediate results at the bedside (quickness), accuracy of results (reliability), the degree of invasiveness to the sick baby is as low as possible (less invasiveness), the examination is not too expensive (cost performance), and the examination can be repeated (repeatability). This book describes the acute phase reactant (APR) score, in which one test item is 10 µL, and three APRs can be measured within 3 minutes in total at the bedside and scored. With clinicians' keen observability and this APR score, neonatal infections can be confidently assessed. In addition, this book does not only refer to APR score, but also publishes the measurement results of cytokine profiles in comparison with APR scores throughout. This book will also increase understanding of the pathophysiology of neonatal infectious diseases.