The reliability and developmental and concurrent validity of the Writing What You Read (WWYR) rubric, designed for use with paper and pen, for hypermedia-authored narrative productions of students in grades 2 and 3 were studied. Sixty students from 4 classrooms produced hypermedia narratives (interactive multimedia presentations) that were rated by 5 trained raters (doctoral students) with knowledge in the teaching of writing process and the use of hypermedia software. The study used an ex post facto design with a comparative component to examine the reliability and developmental validity of the WWYR rubric through percentages of agreements and Pearson correlations. Student achievement was also assessed through the Iowa Tests of Basic Skills (ITBS), and scores from the ITBS and the WWYR were positively correlated. Other reliability and validity analyses suggest that teachers may benefit from applying the WWYR assessment to their students' hypermedia productions. (Contains 7 tables, 3 figures, and 19 references.) (SLD)