The authors describe the use of the CRISPR-Cas9 system to achieve heritable genetic alterations in the germline of *Caenorhabditis elegans*. They designed vectors to express Cas9 and single-guide RNAs (sgRNAs) using a U6 small nuclear RNA promoter, which drives expression in the germline. The system was tested on two genes, *unc-119* and *dpv-13*, where loss-of-function mutations cause recognizable phenotypes. Microinjection of these vectors into wild-type adults resulted in the generation of transgenic animals with targeted disruptions in the germline. The frequency of successful disruptions was between 0.25% and 25% in different experiments, and the resulting mutations were heritable in the F2 generation. The authors also tested the system on two additional loci with no known phenotypes, achieving a higher frequency of disruptions (80.3%, 77.1%, and 18.1% respectively). They confirmed the specificity of the CRISPR-Cas9 system by sequencing the genomes of mutant animals and found no off-target cleavage. The study demonstrates the feasibility of using CRISPR-Cas9 for heritable genome editing in *C. elegans* and suggests its potential for other multicellular eukaryotes.The authors describe the use of the CRISPR-Cas9 system to achieve heritable genetic alterations in the germline of *Caenorhabditis elegans*. They designed vectors to express Cas9 and single-guide RNAs (sgRNAs) using a U6 small nuclear RNA promoter, which drives expression in the germline. The system was tested on two genes, *unc-119* and *dpv-13*, where loss-of-function mutations cause recognizable phenotypes. Microinjection of these vectors into wild-type adults resulted in the generation of transgenic animals with targeted disruptions in the germline. The frequency of successful disruptions was between 0.25% and 25% in different experiments, and the resulting mutations were heritable in the F2 generation. The authors also tested the system on two additional loci with no known phenotypes, achieving a higher frequency of disruptions (80.3%, 77.1%, and 18.1% respectively). They confirmed the specificity of the CRISPR-Cas9 system by sequencing the genomes of mutant animals and found no off-target cleavage. The study demonstrates the feasibility of using CRISPR-Cas9 for heritable genome editing in *C. elegans* and suggests its potential for other multicellular eukaryotes.