This paper presents the results of the characterization of alumina ball size distribution in the mill of a crushing and grinding plant. The mill was unloaded and the balls were sieved. Then, the results were adjusted to three kinds of models; two of them are the traditional models of Rosin-Rammler and Gates-Gaudin-Schumann. The third model applied was the Swebrec distribution function, which has been successfully used on fragmented rock size distribution. The best adjustment for the ball size distribution was obtained by the Swebrec function, with a correlation coefficient of 0.9984.