Virus-induced gene silencing (VIGS) is a fast but transient method for knocking down expression of endogenous genes in plants. Replicating plant viruses activate a defense mechanism called post-transcriptional gene silencing (PTGS), which protects the plant by silencing viral transcripts. VIGS of endogenous genes is accomplished by inserting a gene of interest into a viral vector. When the virus replicates in the plant, PTGS silences both the viral genome and the corresponding endogenous gene. The most robust and widely implemented VIGS system uses tobacco rattle virus (TRV) vectors and N. benthamiana as the plant host. This unit will explain how to introduce TRV-based VIGS vectors into N. benthamiana plants by two methods: syringe infiltration or the Agrobacterium drench method. Furthermore, it will provide two alternate protocols optimized for VIGS in tomato plants: spray inoculation and vacuum infiltration.