Objective - To describe the clinical experience and therapeutic use of fomepizole (4-methylpyrazole [4-MP]) in 3 cats with naturally occurring ethylene glycol (EG) toxicity. Case or Series Summary - All cats were documented to be EG positive by an ethylene glycol test kit. This report describes the dose of 4-MP used, available clinicopathological data, and clinical progression during hospitalization. All patients survived to discharge. New or Unique Information Provided - IV use of 4-MP at 125mg/kg as an initial dose and 31.25mg/kg at 12, 24, and 36 hours is safe and effective for treatment of naturally occurring EG toxicity in cats. Increased HCO3 concentrations were noted after IV use of 4-MP. This is the first report documenting the successful treatment of naturally occurring EG intoxication in cats with 4-MP.