  We solve numerically the Boltzmann equation in the early universe in the
presence of a constant electric field and find the electrical conductivity
$\sigma$ in the range $1\MeV\lsim T\lsim M_W$. The main contribution to
$\sigma$ is shown to be due to leptonic interactions. For $T\lsim 100\MeV$ we
find $\sigma\simeq 0.76T$ while at $T\simeq M_W$ we obtain $\sigma\simeq 6.7T$
