A CRISPR/Cas system was successfully used to efficiently generate targeted gene mutations and corrections in plants. The Cas9 gene was driven by the CaMV 35S promoter, while the chimeric single guide RNA (sgRNA) was driven by the AtU6-26 promoter in Arabidopsis or the OsU6-2 promoter in rice. The engineered CRISPR/Cas system was active in creating double strand breaks (DSBs) when transiently expressed in Arabidopsis protoplasts and stably expressed in transgenic Arabidopsis and rice plants. The system was tested using a split yellow fluorescent protein (YFP) reporter system, which showed a gene correction rate of 18.8% via homologous recombination (HR). The results suggest that the CRISPR/Cas system is highly functional in generating DSBs on target DNA sequences in plant cells and that the DSBs can be repaired by HR to achieve gene correction. The system was used to target endogenous loci in plants, including genes such as BRI1, JAZ1, GAI in Arabidopsis and ROC5, SPP, YSA in rice. These genes were selected due to their obvious growth phenotypes when dysfunctional. sgRNAs were designed to target these genes, and RFLP analysis was used to detect mutations in the target region. Over 50 T1 and 20 T0 transgenic plants were generated for each target in Arabidopsis and rice, respectively. The results showed that a high percentage of the Arabidopsis T1 transgenic plants showed growth phenotypes, with more than 50% of BRI1 plants displaying retarded growth and rolling leaves. For GAI, more than a quarter of the T1 plants showed a dwarf phenotype. For YSA, about 10% of T0 transgenic rice plants showed the expected albino leaf phenotype. The results suggest that the CRISPR/Cas technology will make targeted gene editing a routine practice not only in model plants but also in crops. This study is the first to demonstrate highly efficient targeted mutagenesis in multiple genes in Arabidopsis and rice using engineered CRISPR/Cas. Future studies are needed to examine the germ line transmission and heritability of the CRISPR/Cas-induced mutations and to evaluate any potential off-target effects of the CRISPR/Cas.A CRISPR/Cas system was successfully used to efficiently generate targeted gene mutations and corrections in plants. The Cas9 gene was driven by the CaMV 35S promoter, while the chimeric single guide RNA (sgRNA) was driven by the AtU6-26 promoter in Arabidopsis or the OsU6-2 promoter in rice. The engineered CRISPR/Cas system was active in creating double strand breaks (DSBs) when transiently expressed in Arabidopsis protoplasts and stably expressed in transgenic Arabidopsis and rice plants. The system was tested using a split yellow fluorescent protein (YFP) reporter system, which showed a gene correction rate of 18.8% via homologous recombination (HR). The results suggest that the CRISPR/Cas system is highly functional in generating DSBs on target DNA sequences in plant cells and that the DSBs can be repaired by HR to achieve gene correction. The system was used to target endogenous loci in plants, including genes such as BRI1, JAZ1, GAI in Arabidopsis and ROC5, SPP, YSA in rice. These genes were selected due to their obvious growth phenotypes when dysfunctional. sgRNAs were designed to target these genes, and RFLP analysis was used to detect mutations in the target region. Over 50 T1 and 20 T0 transgenic plants were generated for each target in Arabidopsis and rice, respectively. The results showed that a high percentage of the Arabidopsis T1 transgenic plants showed growth phenotypes, with more than 50% of BRI1 plants displaying retarded growth and rolling leaves. For GAI, more than a quarter of the T1 plants showed a dwarf phenotype. For YSA, about 10% of T0 transgenic rice plants showed the expected albino leaf phenotype. The results suggest that the CRISPR/Cas technology will make targeted gene editing a routine practice not only in model plants but also in crops. This study is the first to demonstrate highly efficient targeted mutagenesis in multiple genes in Arabidopsis and rice using engineered CRISPR/Cas. Future studies are needed to examine the germ line transmission and heritability of the CRISPR/Cas-induced mutations and to evaluate any potential off-target effects of the CRISPR/Cas.