The goal of this project was to identify the lowest effective dilution of antifreeze at the shortest period of contact time to effectively kill adult and juvenile quagga mussels and juvenile zebra mussels. Mussels in various life stages were collected, along with measures of water temperature, dissolved oxygen, conductivity, and pH. Samples were treated with five different dilutions of antifreeze solutions and veligers and mussels were checked for mortality. This assay was successful in examining the toxicity of a propylene glycol based antifreeze across both veliger and adult life stages of dreissenid mussels. Mortality was high in both adults and veligers at very low concentrations. For adults, the chronic LC50 was determined to be 1.87% (p<0.05). The veligers were more sensitive to the antifreeze, with the chronic LC50 determined to be 1.57% (p<0.05). Antifreeze is highly toxic to Dreissena bugensis and is successful in causing high mortality at low concentration.