Not everyone is a friend of the manifold abbreviations that have by now beCome a part of the scientific language of medicine. In order to avoid misunderstanding these abbreviations, it is wise to refer to a reliable dic­ tionary, such as this one prepared by Heister. The abbreviation ED means, for instance, effective dose to the pharmacologist. However, it might also stand for emetic dose. Radiologists use the same abbreviation for erythema dose, and ED could also mean ethyl dichlorarsine. A com­ mon meaning of ECU is European currency unit, a meaning that might not be very often in scientific medical publications. ECU, however, also means environmental control unit or European Chiropractic Union. Hopefully, those making inventions and discoveries will make use of Heister's dictionary before creating new abbreviations when preparing manuscripts for scientific publications. It is a very worthwhile goal not to use the same abbreviation for several different terms, especially if it is already widely accepted to mean only one of them. It may be impossible, however, to achieve this goal in different scientific disciplines. Therefore, although it is wise for the abbreviations used in a publication to be defined, it is also very helpful for readers and writers to use a dictionary such as this one. The author deserves our warmest thanks since we know that compiling such a comprehensive dictionary is based upon incredibly hard effort.