In this project, image registration is used for matching MRI with 3D histology. This match enables the validation of tumor functional characteristic extracted from MRI. At present, results that have been reported are limited to global matching of MRI volumes to small numbers of histological sections. The aim of this work is to develop and implement a method for establishing a detailed 3D relation between in vivo MRI tumor data and histological sections. We use a tight experiment protocol, a dense histological sampling, non-rigid B-spline registration, the utilization of the whole 3D data sets, and the exploitation of an intermediate ex vivo MRI.