  We discuss the optical spectropolarimetry of several core-collapse
supernovae, SN 1996cb (Type IIB), SN 1997X (Type Ic), and SN 1998S (Type IIn).
The data show polarization evolution of several spectral features at levels
from 0.5% to above 4%. The observed line polarization is intrinsic to the
supernovae and not of interstellar origin. These data suggest that the the
distribution of ejected matter is highly aspherical. In the case of SN 1998S,
the minimum major to minor axis ratio must be larger than 2.5 to 1 if the
polarization is 3% from an oblate spheroidal ejecta seen edge on. A
well-defined symmetry axis can be deduced from spectropolarimetry for the
peculiar Type IIn supernova SN 1998S but the Type IIB events SN 1993J and SN
1996cb seem to possess much more complicated geometries with polarization
position angles showing larger irregular variations across spectral features;
the latter may be associated with large scale clumpiness of the ejecta. The
observed degree of polarization of the Type Ic SN 1997X is above 5%. The data
reveal a trend that the degree of polarization increases with decreasing
envelope mass and with the depth within the ejecta. We speculate that Type IIB,
Type Ib, and Type Ic may be very similar events viewed from different aspect
angles.
  The high axial ratio of the ejecta is difficult to explain in terms of the
conventional neutrino driven core-collapse models for Type II explosions.
Highly asymmetric explosion mechanisms such as the formation of bipolar jets
during core-collapse may be a necessary ingredient for models of all
core-collapse supernovae.
