The workshop Computer Science Logic '90 was held at theMax-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). Thisvolume contains 24 papers, chosen by means of a reviewprocedure from the 35 papers presented at the workshop, someof which were invited and some selected from a total of 89submissions. The papers cover a wide range of topics arisingfrom the applications of logic to computer science.