Numerous reports have been presented in scientific periodicals on the occurrence of leukonychia, in which this condition has been treated mainly as a pathologic manifestation of some systemic disturbance. In this report I shall try to show: (1) that leukonychia occurs in a great percentage of all normal people, and (2) that a simple explanation can be formulated for its presence. If the fact is kept in mind that the finger-nail, phylogenetically, is in a disappearing, or at least a transitory, stage of evolution and at best is only a vestige, one can see that it is easily affected by changes in the condition of the body owing to its labile position. This is so well recognized that the nails are regarded as important diagnostic signs in dermatologic and systemic examinations. Leukonychia has been observed as a concomitant phenomenon in various conditions. A few cases of congenital occurrence have been