This article explains the creation and validation of the Narrative Comprehension of Picture Books task (NC task), an assessment of young children's comprehension of wordless picture books. Study 1 explored developmental changes among 158 K-2 children in narrative comprehension and the correlations among children's performance on the NC task and other measures of early reading. There was significant improvement with increasing age on NC task measures. Significant concurrent validity was found between the NC task and oral reading comprehension for readers and between the NC task and several prereading skills for prereaders. Study 2 tested the generalizability of the NC task by giving a sub-sample of students (n = 91) two additional picture books using the NC task procedures. Intertask correlations showed that children were consistent on each of the NC task dependent variables across the three books. The same developmental trends by grade and reading ability were evident on all three versions of the task. Study 3 confirmed the generalizability of the NC task across children, books, and testers, and it revealed sensitivity to longitudinal growth in children's comprehension skills. There was little evidence of practice effects influencing NC scores. Study 3 also revealed significant concurrent and predictive validity between NC measures and other assessments of early reading skills such as the Gates McGinitie Reading Test and the Iowa Test of Basic Skills. The NC task is a valid quantitative measure of young children's comprehension that is sensitive to developmental changes and adaptable to various books. We discuss how narrative comprehension is fundamental to beginning reading and how the NC task may be used for classroom instruction and assessment.