In this tutorial session, we will review case studies in PBPK and QSP modeling and simulation using mrgsolve in R. mrgsolve (https://mrgsolve.github.io) is a free, open-source modeling and simulation platform to support ODE-based model development in R. This content was presented in collaboration with Metrum Research Group, University of Florida Center for Pharmacometrics and Systems Pharmacology, and the ISoP Student Leadership Committee in March 2018.