A program for the evaluation of cerebral blood flow based on the analysis of the time activity curves is presented. The method is based on the Meier and Zierler formula, applying the partition coefficents suggested by Lassen et al. for the corrections deriving from the use of non-diffusible indicators (99Tcm-DTPA). Particular attention is given to the smoothing of the time-activity curve (using Legendre's polynomials) and to the correction function for reflux. The computation procedures and their validity is discussed.