The Bureau of Labor Statistics collects employment figures through two programs: the Quarterly Census of Employment and Wages (QCEW) and the Current Employment Statistics (CES) survey. These two programs collect monthly employment counts from an establishment for the same reference period so the employment figures should generally be identical for each establishment. However, differences exist in the monthly employment figures from the two programs – at the micro and aggregate levels, both at a point in time and in seasonal patterns. Using results from a 2008 response analysis survey (RAS) in which 3,000 establishments with large seasonal differences were asked about reasons for differences in employment reported to CES and QCEW, we analyze the employment differences and potential reasons behind them. The results from the RAS point to a number of different reasons for the seasonal CES and QCEW employment differences. An inconsistent use of the reporting reference period and employment definitions contribute to the seasonal differences between the two programs. In addition, differences in an establishment’s CES and QCEW report preparation procedures, including where the report is prepared and by whom, contribute to the seasonal differences between the two programs.