The dynamics of phase separation for a binary fluid subjected to a uniform
shear are solved exactly for a model in which the order parameter is genera
lized to an n-component vector and the large-n limit is taken. Characterist
ic length scales in directions parallel and perpendicular to the flow incre
ase as (t(5)/lnt)(1/4) and (t/lnt)(1/4) respectively. The structure factor
in the shear-flow plane exhibits two parallel ridges as observed in experim
ent.