This volume constitutes the proceedings of the Fourth International Conference on Integer Programming and Combinatorial Optimization, IPCO '95, held in Copenhagen in May 1995 under the sponsorship of the Mathematical Programming Society. Integer programming and combinatorial optimization provide a fruitful theoretical and algorithmic basis for the solution of a number of optimization problems occuring in real-world situations, such as production planning and scheduling, routing, crew scheduling, or network construction. This volume presents 36 revised papers selected from a total of 105 submissions and offers a representative up-to-date snapshot on the state of the art in this interdisciplinary area of research and applications.