The notions of bipolar fuzzy subalgebras and bipolar fuzzy closed
ideals in BCH-algebras are introduced, and related properties are investigated.
Relations between a bipolar fuzzy subalgebra and a bipolar fuzzy closed ideal are
considered. Conditions for a bipolar fuzzy subalgebra to be a bipolar fuzzy closed
ideal are provided. Characterizations of a bipolar fuzzy closed ideal are discussed.