To implement the North American Industry Classification System (NAICS), the Bureau of Labor Statistics and State partners are assigning NAICS codes to the approximately 8.2 million employers covered by State unemployment insurance (UI) laws. Employer UI reports are the basis of the Longitudinal Data Base (LDB), which serves as the frame for BLS establishment surveys. The NAICS conversion includes a multi-year process of gathering information from employers in order to assign NAICS codes. The collection procedure allows for interim assessment of the effect of the NAICS conversion on industry classification and BLS products. When employers do not provide adequate information for industry classification, BLS will assign NAICS codes based on the distribution of those codes across other establishments with the same Standard Industrial Classification (SIC) and other characteristics. These procedures will be applied to current and, to the extent feasible, historic data on the LDB including establishments that are out of business. This provides a frame for surveys requiring stratification by NAICS and aids in the conversion from SIC to NAICS for ongoing surveys. In addition, the availability of a continuous history with NAICS codes will permit seasonal adjustment and other time-series analysis of the data.