Metallothioneins (MTs) are low-molecular-weight, cysteine-rich proteins that bind to heavy metals. Type-1 MTs function under various abiotic stresses, including exposure to the cadmium ion. We have now isolated the Brassica rapa type-1 metallothionein gene (BrMT1) using yeast systems, and have found that it confers resistance to Cd in otherwise Cd-sensitive yeast. Using a constitutive CaMV355 promoter and an RbsS transit peptide, we successfully targeted BrMT1 to the chloroplasts of Arabidopsis. Overexpression in either the chloroplasts or the cytosol effectively detoxified cadmium and $H_{2}O_{2}$ stresses in transgenic Arabidopsis. In particular, the chloroplast-targeted BrMT1 was associated with a significant reduction in paraquat-induced chlorosis and the accumulation of $H_{2}O_{2}$. This is the first report regarding the effects of type-1 MT1 targeted to chloroplasts. Our results suggest that this may be applicable to the development of plants with enhanced tolerance against environmental stresses.