As atherosclerosis begins in childhood, early diagnosis and treatment of familial hypercholesterolemia (FH) is considered necessary. The basic diagnosis of pediatric FH (under 15 years of age) is based on hyper-low-density lipoprotein (LDL) cholesterolemia and a family history of FH; however, in this guideline, to reduce overlooked cases, "probable FH" was established. Once diagnosed with FH or probable FH, efforts should be made to promptly provide lifestyle guidance, including diet. It is also important to conduct an intrafamilial survey, to identify family members with the same condition. If the level of LDL-C remains above 180 mg/dL, drug therapy should be considered at the age of 10. The first-line drug should be statin. Evaluation of atherosclerosis should be started using non-invasive techniques, such as ultrasound. The management target level is an LDL-C level of less than 140 mg/dL. If a homozygous FH is suspected, consult a specialist and determine the response to pharmacotherapy with evaluating atherosclerosis. If the response is inadequate, initiate lipoprotein apheresis as soon as possible.