The Vienna Component Framework (VCF) supports the interoperability and composability of components across different component models, a facility that is lacking in existing component models. The VCF presents a unified component model-implemented by a facade component to the application programmer The programmer may write new components by composing components from different component models, accessed through the VCF The model supports common component features, namely, methods, properties, and events. To support a component model within the VCF a plugin component is needed that provides access to the component model. The paper presents the VCF's design, implementation issues, and evaluation. Performance measurements of VCF implementations of COM, Enterprise JavaBeans, CORBA distributed objects, and JavaBeans show that the overhead of accessing components through the VCF is negligible for distributed components.