The teleost liver is one of the most sensitive organs to show alteration in biochemistry, physiology and structure following exposure to various types of environmental pollutants. Despite the importance of this organ to environmental toxicology and to ecotoxicology where biomarkers of exposure and of deleterious effect are found, the architectural pattern is not well known. This chapter reviews an architectural plan for teleost liver and compares that to the often cited mammalian pattern. Hepatic tubules composed principally of hepatocytes and biliary epithelial cells are in close proximity to lacunae which are of mesodermal origin. As is described, the tubule and lacunae concepts provide a means to better interpret morphologic alterations following exposure. These concepts are used to illustrate features of the chronic toxicity following exposure to proven carcinogens.