This Special Issue of Journal of Optics A: Pure and Applied Optics is devoted to recent advances in distance measurement techniques. The topic has been discussed at the ODIMAP (Optical Distance Measurements and Applications) Workshops that we have organized in Nantes, France in 1997, and in Pavia, Italy, in 1999 and 2001, the last workshop being attended by more than 120 delegates from all over the world – clear evidence that distance measurement is still a very fertile ground for new ideas and engineering approaches, with a solid history of achievements behind it and a bright perspective of new achievements ahead. Indeed, the story of distance measurement and interferometric techniques is studded with big discoveries and surprising results. We may trace the first ones back to the Michelson interferometer ruling out the ether hypothesis, closely followed by the Sagnac and Fizeau interferometers supplying key results to test relativity. After the invention of the laser, the laser interferometer has become the workhorse of tool-machine and mechanical metrology, while its two-beam counterpart, the laser-Doppler velocimeter as it is called, has filled the need for noncontact, precision anemometry. These two instruments have sold in the thousands of units per year for at least 30 years – a big success and a record in electro-optics instrumentation. Almost contemporary, the measurement of angular velocity through a Sagnac interferometer has generated the ring-laser gyro (RLG) and the fibre-optic gyroscope (FOG) – the heart of the inertial navigation unit (INU) of any modern airliner. Also, since lasers became available, the pulsed and sine-wave telemeters have flourished and provided an invaluable tool both in aerospace and civil topography. Readers may remember the first big science experiment, the Lunar Ranging Experiment (LURE) in 1969, when Apollo 11 astronauts placed several corner cubes on the Moon, and five large telescopes aimed a 1-J Q-switch pulse ruby laser onto them, measuring the Earth–Moon distance with a resolution of 30 cm. Nowadays, telemetry of satellites is a basic tool in geodesy of the Earth, and two years ago the Mars Orbiting Laser Altimeter (MOLE) returned an amazing map of the red planet with 100 m × 100 m pixel resolution. Meanwhile, work is in progress to complete multikilometer arm, atto-meter resolution interferometers intended to sense gravitational waves, with a capability of detecting gravitational collapse of stars megaparsecs away. These developments, and their fallout in industrial applications, are very promising of an exciting prospect for interferometry, range finding, and distance measurement techniques. In this Special Issue we have collected original papers on the different aspects of this field, and we hope this will provide a useful picture of the current state of the art as well as a stimulus for further advances. In closing, we wish to thank Lars Lading, the Editor of Journal of Optics A: Pure and Applied Optics, for accepting with enthusiasm our proposal for this Special Issue, and all the staff at Institute of Physics Publishing for their very effective and professional help throughout the processing of the papers and the shaping of the issue. Special thanks are due to Claire Blay and Joanna Dingley who made our work easy and let us realize why the impact factor of Journal of Optics A has risen so fast. We wish to express our thanks to all the contributing authors, while regretting that several contribution were not back from revision in time to be included in this issue. Editing a Special Issue is a time-consuming exercise, yet very rewarding when it really serves the scientific community. Thus our hope is that this Special Issue on Optical Distance Measurements may stimulate new ideas and further work in our very exciting field.