Model checking technology is among the foremost applications of logic to computer science and computer engineering. The model checking community has achieved many breakthroughs, bridging the gap between theoretical computer science and hardware and software engineering, and it is reaching out to new challenging areas such as system biology and hybrid systems. Model checking is extensively used in the hardware industry and has also been applied to the verification of many types of software. Model checking has been introduced into computer science and electrical engineering curricula at universities worldwide and has become a universal tool for the analysis of systems. This Festschrift volume, published in celebration of the 25th Anniversary of Model Checking, includes a collection of 11 invited papers based on talks at the symposium "25 Years of Model Checking", 25MC, which was part of the 18th International Conference on Computer Aided Verification (CAV 2006), which in turn was part of the Federated Logic Conference (FLoC 2006) held in Seattle, WA, USA, in August 2006. Model checking is currently attracting considerable attention beyond the core technical community, and the ACM Turing Award 2007 was given in recognition of the paradigm-shifting work on this topic initiated a quarter century ago. Here we honor that achievement with the inclusion of facsimile reprints of the visionary papers on model checking by Edmund Clarke and Allen Emerson, and by Jean-Pierre Queille and Joseph Sifakis.