AgentOS is a distributed computing environment or virtual operating system applications using agents. Agents are active, autonomous objects containing both computational logic and state information, with the capability of navigating an agent system such as AgentOS, accessing the services offered by the nodes within the system to complete an assigned task, on behalf of a human user or another agent. AgentOS is a Java-based agent-host that provides support for the execution of agents implemented in Java. The design of AgentOS features a minimal core system that provides an execution model for agents, a network-transparent event-based communication mechanism, and a model for accessing available services. AgentOS is augmented and extended by a system of services, which are implemented as agents themselves. This report provides a description of the agent paradigm and the design of AgentOS.