  We classify the quasi-finite irreducible highest weight modules over the
infinite rank Lie superalgebras $\hgltwo$, $\hC$ and $\hD$, and determine the
necessary and sufficient conditions for quasi-finite irreducible highest weight
modules to be unitarizable with respect to natural $\ast$-structures of the Lie
superalgebras. The unitarizable irreducible modules are constructed in terms of
Fock spaces of free quantum fields, and explicit formulae for their formal
characters are also obtained by investigating Howe dualities between the
infinite rank Lie superalgebras and classical Lie groups.
