The classical triad of McCune-Albright syndrome (MAS) consists of polyostotic fibrous dysplasia (FD), skin hyperpigmentation (café-au-lait spots), and endocrine dysfunction, frequently seen in females as precocious puberty. Patients with MAS display mosaicism of activating somatic mutations of the alpha-subunit of Gs. Thus, the clinical presentation of each individual is dependent on the particular distribution of affected cells, causing a broad spectrum of endocrine and non-endocrine manifestations. Typical endocrinopathies are precocious puberty, hyperthyroidism, growth hormone excess, hyperprolactemia, and hypercortisolism. The onset of these manifestations is usually during infancy and childhood. Since specific treatment is required, the prognosis depends on the severity of each individual endocrine manifestation. Additionally, there are non-endocrine manifestations, such as fibrous dysplasia of bone (FD), renal phosphate wasting, and skin hyperpigmentation, i.e. café-au-lait spots. FD, mostly polyostotic, causes fractures needing surgical and orthopedic treatment. Since previous studies have suggested the overall prognosis of patients with McCune-Albright syndrome to be non-fatal, recent data have drawn our attention to non-endocrine affections, including hepatobiliary dysfunction and cardiac disease, which are probably an important risk factor for early death. In summary, the clinical picture in MAS is related to its mosaic nature, i.e. any cell, tissue and organ in any site of the body could be affected to varying degrees, ranging from one or two mild clinical signs with excellent long-term prognosis to a severe life-threatening multiorgan disease.