[en] Radiation dosimetry is a fundamental part of all radiation protection work. The measurements are made with a variety of instruments, and health physicists, after professional interpretation of the data, can assess the levels of exposure which might be encountered in a given area or the individual doses received by workers, visitors and others at places where the possibility of radiation exposure exists. The types of radiation concerned here are photon radiations, ranging from soft X-rays to gamma rays, and particulate radiations such as β-rays, α-particles, protons, neutrons and fission fragments. The type of technique used depends not only on the type of radiation but also on such factors as whether the radiation is from a source internal or external to the body. Radiation dosimetry is not only used at nuclear facilities; it has diverse applications, for example in determining doses when radiation sources are employed for medical diagnostics and therapy, in safeguarding workers in any industry where isotopes are used, and in assessing the effect of both naturally occurring and man-made radiations on the general public and the environment. The advances of modern technology have increased the variety of sources; an example can be given from colour television, where the high potential necessary in certain colour cathode-ray tubes generates a non-negligible amount of X-rays. The Symposium on New Developments in Physical and Biological Radiation Detectors was one of a continuing series of meetings in which the International Atomic Energy Agency furthers the exchange of information on all aspects of personnel and area dosimetry. The Symposium was devoted in particular to a study of the dose meters themselves - their radiation-sensitive elements (both physical and biological),their instrumentation, and calibration and standardization. Several speakers suggested that the situation in the standardization and calibration of measuring equipment and sources was unsatisfactory, and saw an important role for the Agency in furthering international intercomparison studies. This would in particular help the developing countries who were not able to set up specialized standards laboratories, while providing a check for all Member States on the reliability of quoted measurements and their associated accuracies. The final section on biological dosimetry evidenced the growing interest in this topic. The use of physical dosimeters has certain shortcomings: it is, for example, difficult to determine the dose received by one part of the body from a reading of a dosimeter worn on another part. It is possible that biological changes in the body could be used as a direct measure of the radiation insult received, without the need for interpolating data obtained by physical dosimeters. Biological dosimetry is, however, already being used a a ''null indicator'' in cases of suspected high exposure. This section is rounded off by a brief discussion on general topics related to biological dosimetry. The Symposium was attended by 170 participants from 29 Member States and 5 international organizations. The papers are given in full together with the discussions