Neutron-induced autoradiography was applied to investigate and optimize grain refining in the production of cast aluminium strip. The behaviour of the alloy AlTi5B1 used for grain refining was studied by analysis of both content and distribution of boron. This paper is concerned with the quantitative determination of track density by means of the image analyzer type A 6471 and the results thus obtained in comparison with the amount of tracks visually counted are discussed. Boron contents as calculated from track densities are compared with calibration functions relating track density to the boron content determined by chemical analysis. The content of boron depends upon the position of the autoradiographed plane in the sample, allowing, with its distribution taken into consideration, grain-refining processes to be studied.