In preparation for a planned 2017 American Community Survey (ACS) Mail Design Test of revisions to the mailing materials used to elicit survey responses, the Census Bureau’s Center for Survey Measurement (CSM) provided an expert review of the proposed mail materials and then, after incorporation of comments from the expert review, conducted cognitive testing of the modified ACS mail materials (hereafter referred to as the Full Redesign). This report summarizes the results and recommendations from cognitive pretesting the 2017 Full Redesign materials. Based on cognitive interviews with 25 respondents representing diverse demographic characteristics, CSM recommended several minor modifications to the Full Redesign materials to improve respondent comprehension and liking. Recommendations included decluttering the return address section of the envelopes, adding a thank you to households that have already responded in a reminder postcard that is sent to all sample units, specifying the statutory authority that makes responding to the survey a legal obligation, and moving a sentence many respondents liked from a later mailing to an earlier mailing.