A study examined the ecological validity of five modified measures for children in the prereading and initial reading stages of development. Subjects, 650 students in two cohorts, kindergarten through second grade, were administered modifications of the Early Reading Test (ERT), the Chicago Reading Test (Chicago), the Error Detection Test (EDT), the Weber Test (Weber), and the Eugene Test (Eugene). Results indicated: (1) a strong relationship between the criterion-referenced Chicago test and an individually administered norm-referenced measure of letter and word identification; (2) weaker relationships, especially over time, between the ERT and tests on which children actually read words; and (3) that scores on the EDT, Weber, and Eugene tests showed that children as young as 6 years of age could detect and explain errors in what they read. (Thirteen tables of data are included; 19 references and 4 reading tests are attached.) (RS)