This paper proposed a model for security technology adoption and implementation through the examination of factors affecting adoption and implementation of Public Key Infrastructure (PKI) technology. In the early 1990s, PKI was widely believed to be the panacea for solving a number of security issues that would open the door for business-to-business (B2B) electronic commerce. However, history has demonstrated a lack of broad-based adoption of PKI by organizations, although the use of digital certificates has become fairly prevalent. Why has implementation of the PKI technology been so narrow? What are the factors that mediate security technology adoption and implementation? Technology use, diffusion and adoption literature provide a conceptual framework and theoretical motivation for examining the case of PKI. Additional insight is provided by the examination of the experience of a few organizations that have, to some degree, implemented PKI technology, supplemented by a review of published information on other organizational PKI experiences. The combination of theoretical and practical considerations yield a security implementation model that we believe sheds light on the factors affecting PKI implementation and shows promise for examination of security technology adoption in general. We believe that the model and the research that supports it has important implications for both academics and practitioners in gaining a better understanding of the process for adoption of security technologies by public and private organizations.