In this paper, a new class of sets called pairwise minimal open sets and pairwise maximal open sets in bitopological spaces are introduced and studied. A proper nonempty τi-open subset M of a bitopological space X is said to be a pairwise minimal open (resp. pairwise maximal open) set if any τj-open set which is contained in M (resp. contains M) is either ϕ ( resp. either X ) or M itself. [ABSTRACT FROM AUTHOR]