Purpose: To determine the dose per fraction that could be used when gamma knife or linear accelerator-based stereotactic treatments are delivered in 2 or more fractions. Methods and Materials: The linear-quadratic (LQ) model was used to calculate the dose per fraction for a multiple-fraction regimen which is biologically equivalent to a given single-fraction treatment. The results are summarized in lookup tables. Results and Conclusions: The tables can be used by practicing clinicians as a guide in planning fractionated treatment. For the large doses used in typical stereotactic treatments and for small fraction numbers, the model is not very sensitive to the value of the alpha/beta ratio in the LQ model. A simple rule of thumb is found that for two-fraction and three-fraction treatments the dose per fraction is roughly two-thirds and one-half of the single-fraction treatment dose, respectively. (C) 2003 Elsevier Inc.