RNA interference is a simple, efficient, and highly scalable method for the analysis of gene functions in Caenorhaditis elegans independently of mutants availability (1,2). It is used to study individual genes, gene families, and also for genomewide screenings (3). In a RNAi experiment C. elegans is exposed to double-stranded RNA that corresponds to the sequence of a specific mRNA. This triggers a series of enzymatic processes, resulting in a specific degradation of this target mRNA (4–7). Consequently the animals display a phenotype that results from the depletion of the target protein. The RNAi phenotype can reach the severity of a null mutant (2). Although, generally RNAi is far more effective than antisense RNA (2,8) the effectiveness of a specific RNAi experiment depends on the target gene.