From the 98 presentations of the XIIth Symposium on Colour Vision Deficiencies, 61 were selected after peer review and revision by the authors. In addition to these contributions this volume contains a cumulative index to all authors in the IRGCVD proceedings since the first one in 1968, including the present volume. The contents include contributions on basic questions of anatomical and electrophysiological organisation of the neural pathways underlying colour vision; and on ways in which disturbances of these pathways can produce acquired colour vision deficiencies. Further contributions deal with genetics and congenital red--green colour deficiencies and colour vision testing. The resulting publication contains much of interest to basic vision scientists as well as to specialists in colour vision deficiencies.