A definition and measure for environmental uncertainty are proposed for channels of distribution research. They reflect the notion that environmental uncertainty should be viewed as a perceptual phenomenon experienced through decision-making. Key outcomes of interest that a channel member faces in the decision environment are important components of this construct. Uncertainty is operationalized based on a respondent's lack of information about, and inability to predict the future occurrence of, each outcome of interest. Results of a pilot test support the reliability and pragmatic validity of a modified 18-item measure of environmental uncertainty.