Two studies were conducted to evaluate the effectiveness of using copper sulfate (CuSO4) as a drench in Hampshire ewes to control stomach worms (Haemonchus contortus). A study was conducted to assess the effectiveness of CuSO4 to control gastrointestinal nematodes (GIN) over a three year period. Ewes were FAMACHA scored, hematocrit evaluated for packed cell volume (PCV), and fecal egg counts (FEC) were determined from 2007 through 2009. Ewes received only CuSO4 to control GIN. Ewes with FEC exceeding 6,000 eggs/g feces were drenched. A separate study during the summer of 2008 assessed the potential of CuSO4 drench to cause copper toxicity in Hampshire ewes. Eighty-four ewes were blocked to one of two treatments according to parity and balanced for FEC. One group received CuSO4 (D) and the other was not drenched (ND). Jugular blood samples were collected at pre-determined intervals after CuSO4 was administered to D ewes. Serum was analyzed for aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine kinase (CK). Elevated serum levels indicate copper toxicity. Results suggest CuSO4 has the potential to control stomach worms in Hampshire ewes without causing copper toxicity.