Motion management of intra-fraction tumour motion during radiotherapy treatment can be a challenging task in order to achieve tumour control as well as minimizing the dose to the surrounding healthy tissue. Real-time dynamic multileaf collimator (MLC) tracking is a novel method for intra-fraction motion management that uses the MLC of the treatment machine to reshape the beam to follow the tumour movements. The 3D MLC tracking algorithm recalculates the planned MLC positions using information about the tumour location from an independent monitoring system and the leaves are adjusted accordingly. The over all goals of the studies in this thesis were to evaluate clinical gains of intrafraction motion management with MLC tracking, to investigate which patients that would benefit from this kind of treatment as well as what treatment plans that can be used with this technique.