We use first principles electronic structure techniques to study the magnetic structure of gamma-FeMn using the Korringa-Kohn-Rostocker multiple-scattering approach in conjunction with an extension of the single site coherent potential approximation to noncollinear magnetic structures. Our results show that the noncollinear 3Q and 2Q structures are both stable solutions with the former being slightly lower in energy. The collinear solutions could only be converged in a traditional spin-polarized calculation and are unstable in a noncollinear treatment. (C) 1999 American Institute of Physics. [S0021-8979(99)59008-7].