Drugs-induced liver injury (DILI) can occur through a variety of adverse outcome pathways. Understanding and predicting the effects of multiple toxicity pathways as a function of time and exposure are difficult without systematic organization. Quantitative systems modeling can combine multiple drug effects to address this challenge. The DILIsim Initiative is a public-private partnership involving scientists from 14 major pharmaceutical companies and the FDA; it is now entering its fourth year. In addition to financial support, companies provide often unpublished data and perform in kind research to fill gaps in knowledge. The software produced by the initiative, DILIsym®, is a highly specified, mechanistic, hepatic model that utilizes extensive kinetic information among interrelated biological processes to explore the hepatotoxic underpinnings via simulations. Mechanisms currently included in the model are oxidative stress, mitochondrial dysfunction, bile acid transporter inhibition, and lipotoxicity. The Dilisym® software was originally developed to explain and predict interspecies differences in dose dependent hepatotoxicity to help inform first in man dosing. However, the modeling effort has expanded to improve interpretation of traditional and mechanistic serum biomarkers including miR122, CK18 and its caspase-cleaved fragment, and HMGB1. It is now possible to utilize DILIsym® to predict the range of percent hepatocyte loss through necrosis or apoptosis from measurements of these biomarkers in serial serum samples archived from clinical trials. By varying parameters within Dilisym®, it is possible to create simulated patient populations that mimic selected clinic populations in terms of susceptibility to DILI. This approach successfully recently predicted the latency and incidence of serum ALT elevations that were observed in the clinical trials of troglitazone (ClinPharmacolTher. 96(5):589–598, 2014). Systems modeling tools such as DILIsym® will increasingly be used to support decision making throughout the life cycle of new drug candidates. Drugs-induced liver injury (DILI) can occur through a variety of adverse outcome pathways. Understanding and predicting the effects of multiple toxicity pathways as a function of time and exposure are difficult without systematic organization. Quantitative systems modeling can combine multiple drug effects to address this challenge. The DILIsim Initiative is a public-private partnership involving scientists from 14 major pharmaceutical companies and the FDA; it is now entering its fourth year. In addition to financial support, companies provide often unpublished data and perform in kind research to fill gaps in knowledge. The software produced by the initiative, DILIsym®, is a highly specified, mechanistic, hepatic model that utilizes extensive kinetic information among interrelated biological processes to explore the hepatotoxic underpinnings via simulations. Mechanisms currently included in the model are oxidative stress, mitochondrial dysfunction, bile acid transporter inhibition, and lipotoxicity. The Dilisym® software was originally developed to explain and predict interspecies differences in dose dependent hepatotoxicity to help inform first in man dosing. However, the modeling effort has expanded to improve interpretation of traditional and mechanistic serum biomarkers including miR122, CK18 and its caspase-cleaved fragment, and HMGB1. It is now possible to utilize DILIsym® to predict the range of percent hepatocyte loss through necrosis or apoptosis from measurements of these biomarkers in serial serum samples archived from clinical trials. By varying parameters within Dilisym®, it is possible to create simulated patient populations that mimic selected clinic populations in terms of susceptibility to DILI. This approach successfully recently predicted the latency and incidence of serum ALT elevations that were observed in the clinical trials of troglitazone (ClinPharmacolTher. 96(5):589–598, 2014). Systems modeling tools such as DILIsym® will increasingly be used to support decision making throughout the life cycle of new drug candidates.