The goal of this modelling exercise was to evaluate genetic, nutritional and other factors affecting the distribution of fat in growing and finishing beef cattle. The model had the following objectives: (i) to predict the accretion of total body fat as a function of genotype, sex, implant status and nutrition; (ii) to predict the partition of fat in different depots throughout the animal's lifetime; and (iii) to examine the possible mechanisms for genetic and nutritional differences in fat distribution. This model appears to adequately describe normal growth and accretion fat in the whole body and in the four main depots. It represents a first step in the development of an analytical tool for the study of factors affecting fat deposition and distribution.