Fire design of concrete structures has emerged in recent years as a high profile subject of great interest to both experts and the public. This has been largely prompted by severe damage to concrete in a number of recent tunnel fires, as well as a considerable amount of research and development that has taken place world-wide. fib Task Group 4.3, "Fire Design of Concrete Structures", therefore took the initiative to develop this bulletin in order to present the results of this international research to a wider group of concrete professionals. The report presents a general brief outline of the effect of fire on both concrete material and concrete structures, with emphasis placed on the important developments of the past few years, namely: (a) the increasing use of high strength concrete (HSC) in buildings, tunnels and bridges; (b) the growing acceptance of the use of performance based fire engineering calculations for the structural analysis and design against fire; (c) the problem of, and solutions to, explosive spalling; and (d) fires in tunnels. This report is not intended to be an exhaustive review of the effect of fire on concrete and concrete structures, nor to present a database of properties at high temperature. Instead, the main aims of this document are to present recent trends and developments, highlight key influencing factors, bring together the disparate but related issues in one short document, highlight the deficiencies in current practice and point to the future. The basic principles of performance based codes and fire engineering are also presented on the assumption that the reader is not a specialist in this field.