Ground  penetrating  radar  (GPR)  is  used  to  image pyroclastic density  current  (PDC)  deposits  from  the  May 18th, 1980 eruption of Mount St. Helens. Outcrop verified features  include  a  scour-and-fill  channel  and  a  secondary phreatic  explosion  crater.  Unverified  reflectors  are attributed to either depositional levees or debris avalanche hummocks. This preliminary study validates that GPR can be used to identify and map the three-dimensional structure of  pyroclastic  deposits,  which  increases  our  ability  to develop  robust  interpretations  of  the  mechanisms  and conditions  of  emplacement.  Future  work  is  proposed  to continue  field  investigation  with  high  density  common midpoint  stacking  methods,  tomographic  velocity inversion,  and  seismic methods  to  improve  our  ability  to distinguish between deposits with density, sorting, porosity, and radarfacies.