This paper examines Poland's post-socialist economic transformation from an Industrial Organization perspective. Cluster analysis is used to group sectors which have experienced similar patterns of transformation. The analysis identifies two distinct patterns. Sector restructuring has _ been accomplished largely through firm turnover in the first group. The economic incentives established with the 1990 'Big Bang' reforms have been sufficient to promote restructuring in these sectors. Sector restructuring has lagged in the second group. Industry restructuring has been largely equivalent to firm restructuring. It appears that further institutional reform is required for sector restructuring to take place.