  We have studied ways in which helical primordial magnetic fields could be
constrained by measurements of the cosmic microwave background radiation
(CMBR). If there were helical flows in the primordial plasma at the time of
recombination, they would produce parity violating temperature-polarization
correlations ($C_l^{TB}$ and $C_l^{EB}$). However, the magnitude of helical
flows induced by helical magnetic fields is unobservably small. We discuss an
alternate scheme for extracting the helicity of a stochastically homogeneous
and isotropic primordial magnetic field using Faraday rotation measure maps of
the CMBR and the power spectrum of B-type polarization ($C_l^{BB}$).
