The pathology of farmed tilapias is reviewed from presently available published data. The effects of intensive production systems on the aspects and importance of pathology are outlined. The main pathogenic organisms are recorded. For the moment, these pathogens seem to represent a potential threat, rather than being primary causes of losses. Conversely, environmental factors together with practical errors resulting from a lack of biological and zootechnical data on tilapias, seem to be responsible for most of the difficulties which are encountered. In the short term, intensive research in genetics, nutrition and zootechny should result in significant health improvements for tilapias.