This webinar, led by Dr. Shuhua Hu, introduces the concept of gamma‑distributed delay models and their implementation in PML, the modeling language behind Phoenix NLME and Certara’s R‑based NLME platform. Dr. Hu explains why biological delay processes often occur in PK/PD studies and outlines the limitations of traditional transit‑compartment models. He then demonstrates how gamma‑distributed delays offer a more flexible and realistic alternative, and how they can be efficiently implemented using PML’s delay() and gammadelay() functions. Through practical examples, the session shows how to extend existing models, improve computational speed, and apply distributed-delay methods in real‑world pharmacometric modeling.