Abstract. The use of chemicals to decontaminate watercraft and/or equipment after exposure to zebra mussels Dreissena polymorpha is one method of decontamination that has been recommended by multiple government agencies in the United States. The ideal chemical to be used for decontamination would be inexpensive and easily obtained, would have no or limited effect on nontarget species, and would be relatively environmentally friendly. Two chemicals that have been tested are potassium chloride (KCl) and sodium chloride (NaCl). The toxicity of each chemical to both adult zebra mussels and veliger larvae was examined. Sodium chloride was less effective at causing mortality than KCl within the exposure periods tested. Adult mussels required a 4× longer exposure period to exhibit complete mortality when exposed to NaCl at 30,000 mg/L (24 h) compared to KCl (6 h). At 10,000 mg/L, NaCl took 8× longer (96 h) than KCl (12 h) to cause 100% mortality of adult mussels. Veligers that were exposed to KCl at 1,250 mg/L required a 12-h exposure to attain complete mortality, while those exposed to NaCl at 10,000 mg/L required an 18-h exposure to exhibit the same result. To determine whether KCl is more advantageous as a decontamination chemical, the cost and chemical availability must be researched.