Abstract  This paper presents an object-oriented distributed language, called CUBL++, that is a powerful tool for developing distributed applications on heterogeneous computer networks. CUBL++ is based on objects, called c_units, that communicate through synchronous and asynchronous message passing. A c_unit is an active object composed of data (state) and procedures as traditional (passive) objects, together with the capability of queueing incoming messages, when needed. C_units allow a programmer to implement an application on a heterogeneous architecture, as they communicate with each other without taking into account the physical characteristics of the actual node where they are located. We have experimented CUBL++ on a network where UNIX workstations, WindowsNT personal computers and transputers cooperate in order to perform a given task. In particular, this paper gives a brief description of a distributed system for image processing that has been implemented by using CUBL++.