The liver is responsible for lipid and glucose metabolism, protein and bile synthesis and the biotransformation of xenobiotics. These functions, performed by hepatocytes, are dependent on heterotypic interactions with other liver cell types and the stratified microarchitecture of the organ. In vitro liver models provide insights into the role of each cell type and perturbations upon external stimuli. Despite the dissimilarities to in vivo and rapid dedifferentiation, most liver studies utilize hepatocyte monocultures. These models lack heterotypic interactions causing inaccurate assessments of toxicity and disease. Only a limited number of 3D hepatic models incorporate the major liver cell types, and these cultures primarily focus on the hepatocyte response. We have developed 3D liver models that include all major hepatic cell types and recapitulate the layered architecture of the organ. These models maintain hepatic functions for up to four weeks and can be used to isolate the role and response of each cell type. We used these models to study two critical aspects of the organ -- acute hepatotoxicity and liver fibrosis. There are tens of thousands of chemicals with undetermined effects on the human body. High concentrations of xenobiotics can cause acute liver damage and failure. Liver impairment can result in multiple organ failure, hepatic encephalopathy and death. Therefore, it becomes critically important to investigate hepatotoxicity in a time, cost and resource effective manner. Our 3D liver models were validated for hepatotoxicity testing with acetaminophen, a prototypic drug. We then adapted and optimized the models for high-throughput hepatotoxicity testing with automated procedures and primary human hepatic cells. Liver fibrosis and cirrhosis are well-established consequences of chronic chemical exposure, infection and alcoholism. The initiating factors, end stages and resolution of fibrosis have been extensively studied. However, there is minimal information on the role of the local microenvironment in the progression of the disease from diseased to healthy tissue. We designed 3D liver cultures with a mechanical gradient to gradually model this transition through spatial and temporal perspectives. These findings demonstrate the versatility and accuracy of these 3D hepatic models in the investigation of liver toxicity and fibrosis. / Ph. D.