TWOTRAN, A FORTRAN program for two dimensional transport. TWOTRAN is designed to solve the multigroup discrete ordinates approximation to the two- dimensional Boltzmann equation for particle transport problems in x-y, r-z and r-theta geometries. Three special versions allow for new methods by using the major parts of TWOTRAN. Both direct and adjoint, homogeneous (keff or parametric eigenvalue searches) or inhomogeneous time-independent problems are solved subject to vacuum, reflective, white, periodic, or input specification of boundary flux conditions. Both anisotropic inhomogeneous problems and general anisotropic scattering problems are treated. Arbitrary numbers of groups of up- or down-scattering are allowed.