For seven years, the Test of Adult Basic Education (TABE) was the primary standardized assessment instrument used by the adult education program of the Midwestern Intermediate Unit IV (MIUIV) of the Pennsylvania Department of Education Bureau of Adult Basic and Literacy Education. While reviewing its current assessment procedures, the MIUIV's quality improvement team determined that the Comprehensive Adult Student Assessment System (CASAS) was identified as an "up and coming" adult assessment that warranted further review. The MIUIV's program improvement team therefore decided to conduct an action research project to choose between the TABE and CASAS as its primary standardized assessment instrument. During the project, two pilot sites in the MIUIV's adult education program used the TABE for four months and then switched to the CASAS for all pre- and posttesting for six months. Compared with the TABE, the CASAS took less time to administer and produced slightly less student test anxiety. Nevertheless, the TABE was deemed the assessment instrument of choice based on the following four factors: ability to predict performance on the General Educational Development test; usefulness in planning individual instruction; ease of scoring and communicating results to students; and feedback from students, staff, and the program administrator. (MN)