Theoretical problems involved in the reconciliation of the assumption of constant returns to scale with determinacy of firm size are discussed with particular reference to Australian farms. Various techniques for examining changes in the size distribution of firms are examined and their use demonstrated. The work is stochastic rather than deterministic. B.A.E. sheep industry survey data is used and flock size is used as the measure of farm size. The results do not suggest that inequality in the distribution of farm sizes is increasing. Growth differs between flock sizes within the same region and for the same flock size between regions. Profitability seems to be relatively larger in the medium flock sizes.