This article reviews portal imaging undertaken for prostate cancer with the intention of developing an imaging protocol for this category of patient. It explores the online and offline approaches of electronic portal imaging, when intervention for field placement errors (FPE) should take place and who actually makes this decision. The choice of reference image is discussed and the questions the use of re-simulation. This paper concludes that it is necessary to image for three fractions in the first week in order to highlight systematic errors, that an electronic portal imager is cost effective in time and money, and that radiographers should review images and make the decisions upon intervention strategies. Images will be reviewed via a quantitative template method rather than via a qualitative “eyeball” method.