This article presents case studies of the social shaping of the national union catalog (NUC) in seven countries (four in Central and Eastern Europe, two in the Baltic region, and South Africa). The purpose is to illustrate how technology developments do not occur independently of their social context but rather are co-constituted by the interaction between the various players involved. Interviews with library policy makers and project managers were conducted between 1999 and 2002. The key question investigated is how much of the development of a national union catalog is influenced by choices that are not solely technical but that include players' differing visions, the solutions that they feel they need to adopt, the difficulties they may encounter, and their cultural practices. Findings show that the variety of coalitions and their respective visions and choices have an impact on the conception and design of a national union catalog. The case studies also raise broader issues of technology diffusion, local knowledge, cultural practices, and national identity.