Based on several typical localities of fenites in the world, this paper systematically reviews the petrological characteristics of fenites associated with alkaline igneous rocks and carbonatites. The fenites can be grouped into five types, i. e. , low-grade, medium-grade, high-grade, contact and vein fenites in terms of newly formed mineral assemblages and textures and structures during the processes of fenitization, chemical composition and geological setting and distribution of the fenites as well as the sources of fenitizing fluids. The fenization is controlled by the following factors ; (1) the petrological features and emplacement conditions of the relevant alkaline rocks and carbonatites; (2) the sources, nature and compositions of fenitizing fluids; (3) the mineral assemblage, textures and structures and chemical compositions of wall rocks around alkaline igneous and carbonatite intrusives; (4) physico-chemical conditions during the processes of fenitization. The study of fenites associated with carbonatites is very helpful to recognize the carbonatites whose geological-geochemical signature can be easily affected by late-stage geological processes, so that it difficult to tell them from metamorphic marble of sedimentary origin. It is suggested that a comparison of alkali altered wall rocks around the Bayan Obo Fe-Nb-REE ore deposit with fenites related to carbonatites found in the Bayan Obo area might provide a key clue to the genesis of the deposit, which might show the relationship between the altered wall rocks and fenites.