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The biological rationale for fractionated radiotherapy treatment and the development of noninvasive head fixation systems have led to the increased use of fractionated stereotactic irradiation for intracranial lesions, especially with curative intent. The authors present an overview of the most common immobilization systems with special reference to the evaluation procedures to determine the precision of repositioning. For the different noninvasive head fixation systems used to perform stereotactic fractionated treatments and for several setups, the repositioning accuracy reported is ±1 mm. The maximal displacement observed, 2.3 mm, indicates that these frame types are not suitable for single-fraction treatment. Numerical data are discussed. Finally, the different quality assurance procedures required to perform fractionated stereotactic irradiation are analyzed.