A new method for measuring the dimensions of particle in faeces from lamb is described. The method included a washing procedure by use of nylon bags, freeze drying, dry sieving, scanning and identification of the individual faeces particles use of image analysis. The method is demonstrated on faeces from lamb fed a basal diet of concentrate and hay including the effect of supplementation with whole oat or whole-wheat grain. The distribution of particle length in the individual dry sieving fractions can be described by gamma distribution functions. The distribution of particle length and width was significantly affected by grain supplementation.