  Strong QED has attracted attention recently partly because many astrophysical
phenomena have been observed to involve electromagnetic fields beyond the
critical strength for electron-positron pair production and partly because
terrestrial experiments will generate electromagnetic fields above or near the
critical strength in the near future. In this talk we critically review QED
phenomena involving strong external electromagnetic fields. Strong QED is
characterized by vacuum polarization due to quantum fluctuations and pair
production due to the vacuum instability. A canonical method is elaborated for
pair production at zero or finite temperature by inhomogeneous electric fields.
An algorithm is advanced to calculate pair production rate for electric fields
acting for finite periods of time or localized in space or oscillating electric
fields. Finally, strong QED is discussed in astrophysics, in particular,
strange stars.
