Decision analysts are frequently called on to help inform decisionmakers in situations where there is considerable uncertainty. In such situations, expert elicitation of parameter values is frequently used to supplement more conventional research. This paper develops a formal protocol for expert elicitation with large, heterogeneous expert panels. We use formal survey methods to take advantage of variation in individual expert uncertainty and heterogeneity among experts as a means of quantifying and comparing sources of uncertainty about parameters of interest. We illustrate use of this protocol with an expert elicitation on the distribution of U.S. foodborne illness from each of 11 major foodborne pathogens to the consumption of one of 11 categories of food. Results show how multiple measures of uncertainty, made feasible by use of a large panel of experts, can help identify which of several types of risk management actions may be most appropriate.