The static firm size distributions that we observe in practice are the cumulated result of underlying firm dynamics involving entry of new firms and growth, decline, and exits of incumbent firms. This paper gives an overview of firm size distributions that result as steady states from models differing in the way these firm dynamics are modelled. In the process we (i) propose new functional forms to describe firm size distributions, (ii) give insight in the interrelationships between the distributions in terms of underlying firm dynamics, (iii) give possible firm dynamical interpretations of the parameters of the distributions, and (iv) analyse to which extent the steady-state approach is able to explain the shape of firm size distributions that are encountered in practice. In 2004 an improved version of this report with the title "Firm Size Distributions : An overview of steady-state distributions resulting from firm dynamics models (N200418) was published.