. In this paper we present a new system for non-monotonic reasoning performed using abduction. The system, called ACLP, is a programming language based on the framework of Abductive and Constraint Logic Programming (ACLP) which integrates abduction and constraint solving in Logic Programming. It is build on top of the ECLiPSe language for Constraint Logic Programming (CLP) interfacing (and exploiting) appropriately the non-monotonic reasoning of abduction with the specialized constraint solving of the CLP language. ACLP is intended as a programming language that extends the underlying CLP language in which using NMR (in this case abduction) together with constraint solving it is possible to develop flexible solutions that are computationally viable in the real-life domain. We present the basic theory of ACLP that underlies the system, the main features of the ACLP language and how it can be used when developing applications. We then report on some experiments performed in...