The coextrusion of two polymers in a square channel is presented in this paper. Fluids are fed into the channel through different passages with a plane separating them partway through the channel. Downstream of the separation plane, the streams merge forming an interface between them, which is normally distorted before reaching the exit of the channel. These results show that the degree of distortion depends upon factors in addition to the ratio of the viscosity of the two fluids. The ratio of the flow rates in addition to the shape and location of the separation plane are also important.