New panel data for a large random sample of Estonian firms are used to examine the incidence and dynamics of ownership structures that have occurred since privatization. While there is much path dependence in ownership structures, considerable changes in ownership have also taken place. Econometric findings indicate that (i) inertia in ownership distributions is important, (ii) big firms and capital intensive firms are more likely to be owned by outsiders, (iii) economic performance does not play a decisive role, and (iv) large minority ownership stakes increase the probability that initial majority ownership will change, and, compared to minority ownership by insiders, when outsiders acquire minority ownership positions they are much more likely to eventually assume majority ownership. These results do not confirm the view that there would be a rapid movement toward efficient ownership structures, which underlies much conventional theory on privatization.J. Comp. Econom., September 1999, 27(3), pp. 422–441. Hamilton College, Clinton, New York 13323; and Center for East European Studies, Copenhagen Business School, Dalgas Have 15, 2000, Frederiksburg, Denmark.