The fourth International Workshop on Artificial Neural Networks, now changed to International Work-Conference on Artificial and Natural Neural Networks, will take place in Lanzarote, Canary Islands (Spain) from 4 to 6 of June, 1997. This biennial meeting with focus on biologically inspired and more realistic models of natural neurons and neural nets and new hybrid computing paradigms, was first held in Granada (1991), Sitges (1993) and Torremolinos, Málaga (1995) with a growing number of participants from more than 20 countries and with high quality papers published by Springer-Verlag (LNCS 540, 686 and 930).