The International Society for Clinical Electroretinography provides a link between scientists who are enlarging our understanding of the normal functioning of the visual pathway, and clinicians who investigate and treat visual disturbances. The chief function of the Society is to organize symposia, where, with skill born of long practice, the participants obtain the benefits of both social and scientific contact, without detriment to either. The resulting spread of information is documented both in the society's Newsletter, and by the publication of volumes such as this, the record of the 9th Symposium held at Brighton in 1971. This meeting was a joint Symposium of the ISCERG and the International Union of Physiological Sciences. The subjects covered represent merely the interests of the organizers. The biophysical studies are represented by chapters on such divers topics as the x-ray diffraction of receptor membranes and impedance properties of outer limb suspensions. Other papers deal with the problems of maintaining the retina in vitro in a physiological condition. Papers describing techniques for investigating the functional properties of the visual system shade into those which describe new aspects of human disease. In the past such serendipity has been of value as evidenced by compaHson between this and previous volumes. In 1965 the physiological section of the Proceedings was largely devoted to a new electrical response, the evoked potential of the visual cortex. In this year's Proceedings interest in cortical potentials has moved into the field of practical clinical application. We hope that the more theoretical studies which are described in the present volume will find similar clinical use in the next few years.