Precise localisation of target organs has become increasingly important with the routine use of steep dose gradients from conformal and intensity modulated radiotherapy. This is particularly challenging when soft tissue target organs, such as the prostate, displace relative to bony anatomy. Although novel imaging techniques are being developed for the direct visualisation of such soft tissue structures, contrast and image quality is currently limited. However, the use of radio-opaque intra-prostatic fiducial markers(IPM) during high dose radiotherapy has proven very effective in terms of improving accuracy, and decreasing toxicity.