mathieu used admissible highest weight modules of finite dimensional lie algebras to determine all torsion free modules. there is a natural analogue of admissible modules for affine lie algebras. we use the work of chari, chari and pressley and of rao to construct all admissible modules for non-twisted affine algebras. this involves the construction of all simple highest weight modules for $a_1^{(1)}$in $\tilde{o}$ having finite dimensional weight spaces. we believe that this construction will actually produce all simple highest weight modules in $\tilde{o}$ having finite dimensional weight spaces for arbitrary non-twisted affine algebras. this is joint work with frank lemire