The decrease of positronium (Ps) formation in condensed matter caused by the presence of an external electric field is discussed in terms of the spur reaction model of Ps formation. The rather few experimental results available are shown to be in good agreement with the predictions of the model. Many new results are predicted by use of the available radiation-chemistry results. The work is also a reply to Brandt, who estimated that the spur process of Ps formation is insignificant in hydrocarbons. It is shown that Brandt's estimate disagrees with well established results of radiation chemistry.