This article argues that we know little about whether and how post-communist trade unions mastered the massive task of turning from organizations of communist control over the workplace into representation mechanisms for workers. An initial way to deal with these issues is to re-conceptualize our explanandum from trade union strength to worker interest representation. I use a study of nine factory-level trade unions in the Romanian and Ukrainian metal sectors to explore the merits and the limitations of an approach based on the study of worker interest representation.