Sample attrition, a constant concern in longitudinal studies, occurs when the burden of participation begins to outweigh the rewards (Apodaca, Lea, and Edwards, 1998). Over the past several years, an increasing number of facilities in the annual National Survey of Substance Abuse Treatment Services (N-SSATS) have begun complaining about the burden of yearly participation. In response, Mathematica imbedded an experiment in the 2008 N-SSATS that tested whether prefilling some fields in their annual questionnaire would encourage continued participation. The appeal of such an option was unclear since prefilled questions must still be read and updated, if incorrect.