As the use of web-based surveys grows primarily due to lower costs, concerns of selection bias are increasing, as some people are still not computer or internet literate. The Teacher Follow-up Survey (TFS), a widely used survey of teachers, has undergone similar changes moving from paper to an internet survey. Sponsored by the National Center for Education Statistics (NCES), the TFS is a component of the Schools and Staffing Survey (SASS) designed to determine attrition and mobility rates of U.S. teachers. Designed as a one-year follow-up, the TFS has been administered after each SASS administration since school year 1988-89. Until the 2004-05 TFS, the survey was administered only through paper instruments. Because the 2004-05 TFS was collected by both web and paper instruments and the 2008-09 was primarily collected by web instrument, the authors investigated the possibility that trends could be compromised due to a change in collection mode.