This study explores the readiness factors for the adoption of Internet-based inter-organizational systems (IOS) via a case analysis of fifteen Taiwanese firms. By proposing a three-dimension readiness model (readiness of firm, readiness of partners, and readiness of collaborative relationships), this study extends previous work of IOS adoption to identify critical readiness factors for Internet-based IOS adoption and examines the impacts of these readiness factors on different types of Internet-based IOS adoption, in terms of simple web-based IOS adoption, EOI (EDI on the Internet) adoption, and RosettaNet-based IOS adoption. Three findings are shown in this study: (1) The readiness of firm is an essential condition for all cases, and cases of simple web-based IOS adopters place more focus on firm readiness than other readiness dimensions; (2) EOI adopters places most emphasis on partner readiness, and (3) for the cases of RosettaNet adopters, collaborative relationships is more impor...