  We present a detailed, self-consistent model of radiatively driven stellar
outflows which couples the radiative transfer and hydrodynamics equations. The
circumstellar envelope, which consists of gas and dust, is described as a
two-component fluid to account for relative drifts. Our results agree with both
molecular line observations and infrared continuum spectra, and show that
steady-state outflows driven by radiation pressure on dust grains adequately
describe the surroundings of the majority of cool luminous evolved stars.
