ABSTRACT: This paper reports the first phases of an ACTFL project to develop a computerized adaptive test of reading proficiency. The authors focus on the construct validity of foreign language proficiency as a preliminary step in test development. The theoretical multidimensionality of the construct is clarified, and its implications for test development, item calibration, and validation procedures are discussed. Strategies are specified for selecting text samples, and developing test items which take into account the multitude of text- related dimensions that contribute to variability in proficiency.