['To determine whether palatal medial edge epithelium (MEE) is specialized in its ability to disappear compared with other embryonic, non-palatal, epithelium.', 'Embryonic tissues harvested from CD1 mice.', 'Organs were cultured in 2 ml of DMEM/F12 supplemented with 300 microg/ml L-glutamine and 1% penicillin/streptomycin. Organs were cultured under various conditions including opposing other organs and opposing an inert material for a period of 6 days. Tissues were then processed for histological examination.', 'MEE of shelves opposing nothing persisted, whereas MEE of shelves contacting another shelf disappeared. When a tail was placed against a palatal shelf the MEE disappeared, as did the epithelium from the tail, resulting in fusion between the shelf and tail. Furthermore, when palatal shelves were placed against an inert material the MEE disappeared, suggesting pressure alone is a sufficient stimulus to initiate disappearance of the MEE, and that the interaction between the two palatal shelves is not a prerequisite for the disappearance of MEE. Moreover, when two embryonic tails were cultured in close apposition they fused, as did paired limbs. Non-palatal epithelia also disappeared after contact with inert materials. Epithelial disappearance began within 24 h of contact, but there was an age limit.'] Is tails of the unexpected : palatal medial edge epithelium no more specialized than other embryonic epithelium?