Preliminary measures of pre-purchase uncertainty were developed through focus group interviews and were administered to a nationwide sample of recent appliance purchasers. Responses indicated the presence of two general types of uncertainty: knowledge uncertainty (uncertainty regarding information about alternatives) and choice uncertainty (uncertainty about which alternative to choose). In exploring how each of these uncertainty dimensions was related to search behavior, we found that choice uncertainty appeared to increase search, but knowledge uncertainty had a weaker, negative effect on search. Implications of the findings for previous research on the relationship between uncertainty and search are discussed, along with research directions.