This paper presents an Activity Theoretical analysis and design model for Web-based experimentation, which is one of the online activities that plays a key role in the development and deployment of flexible learning paradigm. Such learning context is very complex as it requires both synchronous and asynchronous solutions to support differenttypes of interaction, which can take place not only among users but also between the user and the provided experimentation environment, and also between different software components that constitute the environment. The proposed analysis and design model help clarify many concepts needed for the analysis of a Web-based experimentation environment. It also represents an interpretation of Activity Theory in the context of Web-based experimentation.