Introduction generale a la classification, la terminologie morphologique, l ontogenese et evolution des acariens. - The present paper is the text of an address delivered to the French acarologists on the occasion of their first meeting. It consists of an introduction to the classification, the morphological terminology, the ontogeny, and the evolution of mites. The following classification is introduced here. Subclass: Acarida. Superorders: Anactinotrichida and Actinotrichida. Orders: Opilioacarida, Holothyrida, Gamasida, Ixodida (Anactinotrichida); Actinedida (= Trombidiformes), Oribatida, Acaridida (Actinotrichida). The ending ina is proposed for the suborders (Gamasina, Liroaspina, Uropodina, Antennophorina; Argasina, Ixodina; etc.). A survey is given of the main characters seperating the two superorders. The introduction to the general morphology deals with soma-terminology, segmentation of the body, gnathosoma, segmentation and articulation of the appendages, and general chaetotaxy. The terms gnathosoma, idiosoma, prosoma, opisthosoma, and podosoma (although dorsally ill-defiued) are accepted here; the terms proterosoma, propodosoma, metapodosoma, and hysterosoma are dissuaded; stethosoma ( = prosoma without gnathosoma) is introduced as a new term. Directions are given for the orientation of figured structures; a general use of the same series of abbreviations is recommended. A general nomenclature for the postembryonic ontogeny, including a clear distinction between stase and stage is also recommended. The study of evolution by comparison of ontogenies is briefly explained. Attention is drawn to the value of the investigation of the phylogeny of characters and the reconstruction of archetypes for the creation of a natural classification.