Recent research on the impact of cell phones has largely focused on coverage and nonresponse error with few exceptions (Kennedy et al 2009, Brick et al 2011). In this work the authors focus on nonsampling error in the American Time Use Survey (ATUS). This nationally representative survey is conducted by the U.S. Census Bureau on behalf of the Bureau of Labor Statistics. The sample for the ATUS is derived from households that have completed Wave 8 of the Current Population Survey. Households that volunteer a phone number for that survey are then called for the ATUS using that phone number (those who do not volunteer a phone number are mailed an invitation to participate and an incentive). The vast majority of CPS respondents provide Census with a phone number. The ATUS further selects a sample member from within the household to answer relatively detailed questions including a 24 hour time use diary. In this work we examine the impact of calling cell phone numbers on nonresponse and measurement error in the ATUS. Because the sample is derived from CPS completed interviews, we are able to model nonresponse using CPS data. Almost 40% of ATUS telephone sample volunteered their cell phone number for contact in the CPS. Those who volunteer their cell phone number for survey contact in the CPS are just as likely to say that a phone interview is acceptable. Cell phone volunteers are less likely to be complete ATUS interviews due to noncontact while their refusal rate is similar to those volunteering a landline number. Differences in measurement error appear to be negligible. There are some differences in the estimates of time use, but these are largely due to demographic differences.