This volume contains the proceedings of the fourth conference on Parametric Optimization and Related Topics, held in Enschede, The Netherlands, from June 6-9, 1995. Parametric optimization, as a part of mathematical programming, investigates the behaviour of solutions to optimization problems under data perturbations. Properties involved, such as continuity, differentiability, topological stability and structural stability play a fundamental role in a series of further questions that are of interest both from a practical and a theoretical point of view. Many connections with other disciplines of operations research, like stochastic programming, model-building, numerical methods and optimal control, originate from these properties. The presented papers (all refereed) are topical and original studies reflecting recent results in current directions of research in theory and applications.