"Central core disease" (CCD) is a rare disease of infancy and childhood and represents the prototypic member of a group of muscular disorders known as "congenital, benign (non progressive) myopathies". It is very uncommon to diagnose cases affected by CCD in youth and adulthood. The disease is mainly familial with a dominant autosomal pattern of inheritance, but sporadic cases are known to occur. The candidate gene has been localized on chromosome 19q13.1, and is allelic with RYR-1 ("ryanodine receptor" [calcium release channel gene]), the gene responsible of the susceptibility to malignant hyperthermia. In some familial cases of CCD a susceptibility to malignant hyperthermia was also recognized. The diagnosis is only made based on muscular biopsy, which documents some peculiar morphological abnormalities, i.e. focal losses of oxidative enzyme activities, exclusively in type I muscular fibres. The basis for the loss of such activities is represented by an almost total absence of mitochondria and sarcoplasmic reticulum in those focal regions of muscle fibres. Cores may be "structured" and "unstructured" based on the reactivity with myosin ATPases, which ultrastructurally means preservation or destruction of myofilaments. Both structured and unstructured cores qualify this disease in the same way. The authors have observed two cases of CCD in patients in their non infantile age. Both diagnoses were accomplished by means of muscular biopsy, and the results of their studies in both cases are herein presented and discussed.