Road salt application and resulting entrance of salt-laden runoff into streams are common winter events, yet little information exists about their influence on lotic periphyton function. We measured extracellular enzyme and photosynthetic activities of natural winter lotic periphyton communities under various short-term laboratory salt exposures. Short-term exposure to increased concentrations of salt reduced the photosynthetic activity of the periphyton but photosynthetic activity was restored by replacing saltamended water with ambient stream water. Salt exposure also reduced periphytic -glucosidase activity but not the activity of phosphatase or leucine aminopeptidase. Elevated, but realistic, short-term salt exposures reduced the functioning of lotic periphyton communities. Further work will be necessary to understand the long-term effects of increased salt concentrations on periphyton and extracellular enzyme activity.