Toxicologic pathology is a classical discipline in the toxicology arena, and despite various emerging techniques, still is a major cornerstone in the process of hazard identification and risk characterization. Most knowledge derives from laboratory animal studies and, to a lesser extent, human data. Currently interest is growing in applying toxicological pathology for lower animals, in particular fish as being the most developed aquatic genus. This is triggered by the interest in so-called endocrine disrupting chemicals (endocrine disrupters, EDCs), xenobiotics that interfere with the endocrine system and thus may affect reproduction and/or development, and for which pathology is an essential technique in general in vivo studies. As the aquatic ecosystem is a major recipient of pollutants, fish constitute an important potential target and can be used as a research and bio-monitoring tool. For this goal knowledge of the pathological responses of fish to EDCs is essential and therefore we have studied the responses of laboratory fish to a set of reference endocrine modulating chemicals. In this paper, such effects are compared with known response patterns in mammals, thereby accounting for the specific aspects of anatomy and physiology in fish.