This volume contains many of the papers presented at the conference "Optimum Design 2000: Prospects for the New Millennium" held in Cardiff, UK on April 12th - 14th, 2000. The majority of the papers consider aspects of optimum experimental design from the theoretical to applications. Many of the optimisation problems arising in the optimum design theory in general and the articles in this volume in particular, fall into the category of nonconvex, including global, optimization. The papers are organised in two sections. Since we are at the beginning of a new millennium the first paper starts by looking back at the beginnings of optimum exper­ imental design in 1917 and sketches the development up to Kiefer's paper read to the Royal Statistical Society in 1959. This is the first in a group of papers which we have labelled "Theory", which cover the more general aspects, such as the properties and methods of construction of designs. In the "Applications" section there are papers on sequential design problems arising in the pharmaceutical industry and on the designs with discrete factors which occur in agriculture. There are also papers on training neural networks, on the efficient design of sampling methods, on design problems in mixtures, arising from a study of glass manufacturing, and on the resistance of Brazilian weeds to herbicides. The number attending the meeting was deliberately limited to 50 in order to encour­ age a workshop atmosphere and the exchange of ideas.