The process of developing agent based applications requires at least two tasks that are usually tackled separately by programmers. On one hand, programmers need to develop business rules and other support tasks for agents. On the other hand, programmers need to develop user interfaces (UI) for agents in order to enable end users (not only owners but also other third parties) to interact directly with them. The paper focuses on this second task (developing user interfaces) and describes the solutions offered by the AgentSpace mobile agent system (A. Rodrigues da Silva et al., 1998). Basically, we present and discuss two complementary ways to gather user interfaces with mobile agents. On the one hand, mobile agents don't provide any UIs. This situation promotes the separation of the UI and the backend (i.e., the agent) which allows flexibility and reuse. On the other hand, mobile agents provide by default UI components, which consequently promotes agents as better units of development and management. This situation can be very suitable in the context of dynamic, large scale applications such as those found in telecommunication and e-commerce domains.