INTRODUCTIONThis protocol describes how to produce gene knockdown in planarians using RNA interference (RNAi). It is a standard technique to evaluate gene function during regeneration and tissue maintenance in planarians. The procedure involves microinjecting double-stranded RNA (dsRNA) synthesized in vitro. Depending on the gene target, this technique can produce robust phenotypes that can be further evaluated by diverse macroscopic or microscopic procedures.