  Linear spectropolarimetry is a powerful tool to probe circumstellar
structures on spatial scales that cannot yet be achieved through direct
imaging. In this review I discuss the role that emission-line polarimetry can
play in constraining geometrical and physical properties of a wide range of
circumstellar environments, varying from the accretion disks around pre-main
sequence T Tauri and Herbig Ae/Be stars, to the issue of stellar wind clumping,
and the aspherical outflows from the massive star progenitors of supernovae and
long gamma-ray bursts at low metallicity.
