This paper briefly reviews the application of histopathology as aninstrument or endpoint in toxicity studies in fish. For long this has been applied rather occasionally in (regulatory) toxicology, and was mainly of interest in fundamental studies and limited carcinogenicity experiments. However, nowadays there are various incentives that ask for the application of pathology, such as field monitoring of pollution effects, the wish for optimal use and lower species of laboratory animals, the availability of modern histology techniques, and insight and interest in mechanistic data. This is timely illustrated by the current broad interest in endocrine disrupting pollutants-a threat mainly in the aquatic environment-where histopathological organ and tissue changes in intact sentinel fish species provide pivotal diagnostic and mechanistic features.