Going back to discussions at the 2002 International Nonresponse Workshop (organized by Bob Groves and Lars Lyberg), it has become a Best Practice to incorporate nonresponse bias studies into survey designs; e.g., OMB has issued a directive that any federal survey that expects less than an 80% response rate should contain a study of nonresponse bias. Thus nonresponse bias studies have started to be reported, including those that attempt to gather new data from the original study’s responders/nonresponders. However, few of these types of nonresponse bias studies achieve a near perfect response rate. We will report findings about nonresponse and nonresponse bias in a nonresponse bias study. These data come from a 2011 survey conducted with existing panel members which followed up responders and nonresponders to a prior 2011 study in which they were invited to join a new measurement panel. In the original study, a random national sample of 400 households was drawn from KnowledgePanel®, a probability-based online panel. One-third of that initially designated sample completed the original questionnaire to determine their eligibility and consent to participate in the measurement panel. This yielded an AAPOR RR1 of 33.5%. After the recruitment period for the original study ended, all 400 household were invited to complete a nonresponse bias follow-up questionnaire. This follow-up survey achieved a 75.5% AAPOR RR1. A host of demographic and psychographic variables on all 400 households was known from other questionnaires these households previously have completed. We will report findings on the nature of the nonresponse in the original study (2/3 of which were nonrespondents) and the nature of the nonresponse to the follow-up nonresponse study (1/4 of which were nonrespondents). To our knowledge, this will be the first time findings will have been reported on the nature of nonresponse bias in a nonresponse bias study.