Several agent platforms of general purpose exist - for example, Voyager, Jade, and Grasshopper - each of which provide an environment for building and executing software agents. Unfortunately, the platforms are usually incompatible with each other. Thus, agents built for one platform cannot be used in another platform, nor can they interact with agents in other platforms. Some effort is put into standardizing agent communication and migration in FIPA and in OMG, but these standards are not yet supported by most of the existing platforms. Therefore, we should find some other ways to allow interaction between agents in different platforms.In this paper we will show that it is possible to make platform independent agents that are able to migrate between incompatible platforms. We will also describe how messages can be delivered to agents in other platforms, and show how to build platform independent service agents that are used via method calls. The ideas have been tested in practice with Voyager, Jade, and Grasshopper platforms.