Red deer ( Cervus elaphus L.) are known from many prehistoric sites in Western Europe; a number of these are usually of great size as compared with contemporary animals. This essay is an attempt to summarize the literature concerning the size of the prehistoric red deer in comparison with the recent species and to discuss the different influences of the habitat (extent and character of the biotope, food, climate) on the dimensions of red deer. It is the intention that it should attribute to a better understanding of the factors that may have caused the great size of many prehistoric red deer and to try and find out if a similarity between the variation during the course of postglacial times and the local variation in relation to the habitat exists. Most investigators agree that the prehistoric red deer belongs to the same species as the recent red deer. Cervus elaphus L. The red deer from Western and Central Europe (France, the Netherlands, Belgium, Luxembourg, Denmark, Switzerland. Germany, Italy, the Balkans and Western Russia) are usually considered to be all of the same subspecies C. elaphus hippelaphus ERXLEBEN, 1777 (e.g. HALTENORTH & TRENSE, 1956). Within this subspecies a number of varieties can certainly be distinguished according to different habitats, but, as will be clear at the end of this article, it is likely that most of their differences are only phenotypical. On the other hand some investigators distinguish quite a lot of subspecies. The first thing to be demonstrated here is the fact that most prehistoric red deer are indeed considerably larger than the present red deer. RÜTIMEYER (1861, p. 59, 60) pointed out that remains of red deer recorded from the Swiss lake-dwellings are about one third larger than the corresponding parts of recent species of C. elaphus in Switzerland. RITCHIE (1920, p. 336) is also of the opinion that red deer were about one third larger in former times than a well developed animal of today. RITCHIE based his conclusion on the following prehistoric finds: three antlers and one complete skeleton. VAN GIFFEN (1913, p. 135, 136) likewise reports the large dimensions of some scanty remains of red deer known from the Dutch terps (including a mandibula). According to INGEBRIGTSEN (1923, p. 204, 205) WAHLGREN holds the opinion that the size of the recent red deer and of the prehistoric ones can easily be explained by differences in environment and age. INGEBRIGTSEN himself on the other hand thinks that it is clearly demonstrated by the investigations of BRINKMANN that subfossil red deer were indeed larger than the recent ones. BRINKMANN poses the idea that measuring teeth is very useful to compare sizes of deer; when measuring a molar one is independent of the age of the animal in question and to a certain degree independent likewise of the influences of the environment. For when a molar is fully developed it will not increase in size any more, even when the animal in question has not yet stopped growing. The size of the teeth therefore are a standard for the size which the animal can attain when conditions are normal. When the teeth are larger and better developed, the deer in question will be larger and better developed too. On account of BRINKMANN’S assertions that measuring teeth is the most proper method to prove that subfossil red deer were of greater size than the now living specimens, INGEBRIGTSEN has been measuring the M3 of the lower jaw of subfossil and recent red deer; it has become clear that subfossil deer were indeed larger (cf. the following table; though the animals are supposed to differ one third in lenght, the molars do not shows this difference). At the same time it should be born in mind that also smaller prehistoric remains of red deer exist. Probably there was a large variation in size in those times too, as it appears from my own observations.2) Lenght M3 (mandibula) of Cervus elaphus L.