Mastocytosis refers to a heterogeneous group of clinical disorders characterized by an abnormal accumulation of mast cells (MCs) in various tissues. The skin is the organ most frequently involved, but all organs may be affected. The clinical signs and symptoms are produced by the functional effects of mast cell-derived mediators and the anatomical distribution of the mast cells. The 2008 WHO-classification defines 7 categories of mastocytosis. Skin disease, with or without systemic involvement, is by far the most common form of childhood mastocytosis. Measurement of serum tryptase is important in the diagnostic algorithm of pediatric mastocytosis. In children with tryptase <20 ng/mL, the diagnosis of cutaneous mastocytosis (CM) may be decided upon without bone marrow examination (BME), unless other signs of SM are present. If the baseline tryptase level exceeds 100 ng/mL, a BME should be considered regardless of age. If the serum tryptase is 20-100 ng/mL in children without other signs of SM, the provisional diagnosis "mastocytosis in the skin" (MIS) can be established and monitored until puberty. If MIS remains present after puberty, a BME should be performed. In adult-onset mastocytosis a complete staging and application of the systemic mastocytosis criteria should always be performed. Treatment is mainly directed at alleviation of symptoms. As c-kit mutations prove to be very important in the pathogenesis of mastocytosis, targeted therapies using kit inhibitors may evolve as important future therapeutic options.