Comparison tests are reported of the use of a twin palm print collection to evaluate the influence heredity has on palmar flexion crease path and configuration and to assess their uniqueness and persistency to determine if palmar flexion creases have the ability to individualize and thus qualify as a suitable personal identification medium. When applied to the identification process, palmar flexion creases are a suitable method of personal identification alone or when used in conjunction with friction ridges. They are sufficiently persistent and variable to individualize. Skin folds also are sufficiently variable for individualization and are persistent as long as deformation of the part does not occur. 8 figures, 3 tables, and 11 references