The ontogeny of the digestive tract of marine fish larvae has been the subject of many studies these last twenty years. Beyond the scientific interest for such animal species, particularly for developmental aspects, most of these studies aimed to come up with the expectations of commercial hatcheries by reducing the bottlenecks in larvae culture and weaning processes (switch from live preys to compound diet feeding sequence). Consequently, the profile and dietary adaptation of digestive enzymes, the description and histology of the main organs have been extensively studied, when others aspects of the physiology of the larvae digestive tract (gut hormones, intestinal transport…) were poorly investigated and this imbalanced knowledge is showed through this review. For a long time, it has been hypothesized that marine fish larvae had insufficient digestive enzyme capacity to handle compound diets compared to juvenile fish, and several weaning strategies were built on the supply of exogenous enzymes (Kolkovski, 2001) but were never very conclusive. More recently, it was considered that ontogenetic differences between the larval type and adult type organ function do not mean that larvae face physiological or digestive deficiencies during early life stages. Fish larvae should not be considered as primitive organisms but represent a transitional period in which both ontogeny and growth cause substantial changes in structure, physiology, size and body shape. The basic mechanisms of organ development are similar in all teleosts, even though there are considerable differences regarding the relative timing in the ontogeny. The time in organ development and its associated physiological functions is affected by the general life history of each species and a number of abiotic and biotic factors, such as water temperature, food availability and composition during early life stages. These changes determine the nutritional and physiological performances of a fish, and therefore its ability to deal with challenges during its subsequent life (Fuiman, 1997). According to these previous considerations, it has been considered determining to take into account the digestive features of the marine fish larvae for formulating compound diets, in the view to promote the larvae growth and facilitate the settlement of an adult mode of digestion (Zambonino Infante et al., 1997; Cahu et al., 2003). The knowledge about the ontogeny of the gastrointestinal tract has gained by the association of different analytical approaches, from classical histology to molecular approaches, including immunohistochemical and biochemical research. These studies have demonstrated that marine fish larvae constitute a very interesting animal model to study the interactions between nutrients (exogenous nutrition) and the developmental processes. Therefore, the potential applications of studies on the ontogeny of the gastrointestinal tract in marine fish larvae go beyond the field of fish aquaculture, .with possible applications to human health (Marza et al., 2005). This review aims to summarize the informations available on the morphological and functional changes occurring in the main organs of the digestive tract of several species of marine fish larvae, and examine the factors regulating these changes.