This document summarizes the use of the nematode C. elegans as a model organism for studying human diseases. It discusses how CRISPR/Cas9 can be used to introduce disease-related mutations into C. elegans to model retinitis pigmentaria, cancer, and responses to chemotherapy. Drug screens and RNAi screens in these mutant worms have identified genetic modifiers and potential drug targets for treating human diseases. The small size, rapid life cycle, and genetic tractability of C. elegans make it a valuable pre-clinical model for validating targets and precision medicines before testing in mammalian systems.