This study examined the toxicity and accumulation of copper in the livers and kidneys of Long-Evans rats after a subacute exposure to copper dimethyldithiocarbamate (CDCC) wood preservative. CDDC was recently introduced as an alternative to chromated copper arsenate (CCA) preserved wood. Female rats (220–270 g) were treated with 0, 25, 50, or 75 mg/kg CDDC by oral gavage for 3 wk. Light microscopy revealed that higher doses of CDDC induced diffuse necrosis and a loss of sinusoids in the livers of Long-Evans rats with vacuolization in the highest dose. Rats treated with 25 mg/kg CDDC displayed a thickening of the basement membrane of Bowman's capsule and the mesangium. Exposure to higher CDDC concentrations (50 and 75 mg/kg) showed moderate to marked expansion of the mesangial matrix and glomerular necrosis with an overall loss of glomerular structure seen in the highest dose. The concentration of copper was significantly increased in the tissues of animals exposed to CDDC in a dose-dependent manner. Western blot analysis revealed the induction of the stress protein Hsp70 and the formation of 4-hydroxy-2-nonenal (4HNE) adducts in liver and renal tissues, indicating peroxidative damage. CDDC was shown to be toxic to the livers and kidneys, at all doses used, and this toxicity is related to peroxidative insult.