With the exception of the skill, the bones have more varieties of lesions about which little or nothing is known than do any other tissues of the body. While mast of these lesions, known largely through their roentgenological appearance and empirical course, are rare, the total group is numerous enough to engage the interest of many. Any approach to useful classification or increased understanding of etiology or pathogenesis would be welcome. Whether Rubin's novel approach fulfils this need in any measure is problematic.