the workshop computer science logic 90 was held at the max-planck-haus in heidelberg, germany, october 1-5, 1990. it was the fourth in a series of worskhops, following csl 89 at the university of kaiserslautern (see lncs 440), csl 88 at the university of duisberg (see lncs 385), and csl 87 at the university of karlsruhe (see lncs 329). this volume contains 24 papers, chosen by means of a review procedure from the 35 papers presented at the workshop, some of which were invited and some selected from a total of 89 submissions. the papers cover a wide range of topics arising from the applications of logic to computer science.