This volume contains the proceedings of FORTE 2003, the 23rd IFIP TC 6/ WG 6.1 International Conference on Formal Techniques for Networked and D- tributed Systems, held in Berlin, Germany, September 29-October 2, 2003. FORTE denotes a series of international working conferences on formal descr- tion techniques (FDTs) applied to computer networks and distributed systems. The conference series started in 1981 under the name PSTV. In 1988 a s- ond series under the name FORTE was set up. Both series were united to FORTE/PSTV in 1996. Two years ago the conference name was changed to its current...