Clinical prediction rules (CPR) are tools including appropriately weighted clinical aspects (history, physical examination and/or complementary tests) showing the odds for a specific diagnosis or prognosis. Their development includes a complex and strict process to achieve the scientific strength which supports use in clinical settings. Although CPR may be developed for almost any clinical situation, they are particularly useful in complex decision making, high-risk situations and for health cost reduction. Most CPR in pediatrics are devoted to infectious diseases, but only a few of them are used in daily practice. Reluctance in using them may be related to the most pediatrician's expectation of 100% sensitivity, when only a few CPR have sensitivity >90%. It is important to take into account that even a less-than-perfect CPR may be more sensitive than the physician's clinical judgment alone.