Although the Census Bureau would like to reduce paper use as well as costs by moving from a paper form to an online version of the Decennial Census, there is concern that many United States residents to do not have internet access and it is uncertain whether the situation will change before 2020. Additionally, there is evidence that offering both a mail and an internet option for taking a survey actually lowers the response rate (Smyth, Dillman, Christian and O‘Neill, 2010). The Census Quality Survey (CQS) was conducted in order to estimate measurement error, such as simple response variance, from a census Internet questionnaire compared to that from a census paper questionnaire (Hill, J., Reiser, C., and Bentley, M., 2010). When considering an online version of the Census, its overall usability must be taken very seriously, especially for an instrument that needs to be completed by every resident of the United States. For a data-collection Web survey to be successful, its user interface must support the user in completing the survey in an efficient, effective, and satisfying way. The Census Bureau‘s Usability Lab conducted two rounds of usability testing of the online Census CQS instrument in April and June of 2010. The goal was to identify elements of the user-interface design that were problematic and led to ineffective and unsatisfying experiences for potential respondents of the survey. Usability issues identified during testing (such as participants having trouble with the auto-tabbing functionality of the ―Date of Birth‖ question) will be discussed along with potential suggestions for the improvement of future online surveys.