Abstract The large Pleistocene herbivores of Mediterranean islands belong to four families: Elephantidae, Hippopotamidae, Cervidae and Bovidae. They originated in environments characterized by peculiar features, different from the typical habitats of their ancestors. This paper examines some aspects of the functional morphology of these endemic forms in relation with their environment. Lightening of limbs in elephants are essentially related with size reduction, which allows to move on uneven and steep grounds. Adaptations in hippos to a more arid environment and uneven grounds are also shown by specimens with scantily reduced size. Morpho-functional variations in cervids are connected with the life habits rather than body size; the various forms are characterized by a wide spectrum of adaptations. Modifications in endemic bovids are less known with exception of the dwarf balearic bovids, in which the evolutionary process produced a loss of agility and speed. Changes in size and in functional morphology are always quicker and dependent on the interaction of several factors. In the evolution of the endemic herbivores various phenomena have to be considered: neoteny, achondroplastic dwarfism, hypermorphosis. The presence/absence of large carnivores has a stronger influence on the dimensional and morpho-biometric variability than on the body size reduction. Riassunto I grandi erbivori pleistocenici delle isole del Mediterraneo sono in genere caratterizzati da variazioni di taglia e di morfologia in parte dipendenti dalle diverse dimensioni corporee acquisite, in parte legate a nuovi modi di vita. Tali elementi hanno diversa incidenza nei processi evolutivi dei singoli taxa, in funzione dell'interagire di vari parametri, ma in genere sussiste in ambiente insulare una stretta relazione tra condizioni fisiografiche e morfologia funzionale.