In this technical report, we describe a study examining the internal structures of the easyCBM reading measures, Grades K-5. Data were gathered from a convenience sample of 114 Kindergarten students, 43 first graders, 82 second graders, 100 third graders, 109 fourth graders, and 71 fifth graders attending schools in Oregon, Georgia, South Carolina, Idaho, Florida, California, Pennsylvania, and Kentucky. Students were administered a variety of easyCBM reading measures (Phonemic Segmentation, Letter Names, Letter Sounds, Word Reading Fluency, Passage Reading Fluency, and Comprehension in Grades K-2; Word Reading Fluency, Passage Reading Fluency, and Comprehension in Grades 3-5) in a three-week period in November of 2011. Confirmatory factor analysis was used to test the factor structure at different grade bands. For students in the Grade K-2 sample, a three-factor model of reading (where Phoneme Segmentation, Letter Names, and Letter Sounds loaded on "early literacy," Word and Passage Reading Fluency loaded on "Fluency," and both types of comprehension measures loaded on "Comprehension") produced the best fit. For students in the Grade 3-5 sample, a two-factor model (where Word and Passage Reading Fluency loaded on "Fluency" and the different kinds of comprehension measures loaded on "Comprehension"), with testlet effect produced the best fit. Appendices are as follows: (1) One-Page Recruitment Flier; (2) Teacher Instructions: Grade K-2 Sample; (3) Teacher Instructions: Grade 3-5 Sample; (4) Individually-Administered Measures, K-2 Sample, Assessor Copies; (5) Individually-Administered Measures, K-2 Sample, Student Copies; (6) Group-Administered Measures, K-2 Sample; (7) Individually-Administered Measures, Grade 3 Sample, Assessor Copies; (8) Individually-Administered Measures, Grade 3 Sample, Student Copies; (9) Group-Administered Measures, Grade 3 Sample; (10) Individually-Administered Measures, Grade 4 Sample, Assessor Copies; (11) Individually-Administered Measures, Grade 4 Sample, Student Copies; (12) Group-Administered Measures, Grade 4 Sample; (13) Individually-Administered Measures, Grade 5 Sample, Assessor Copies; (14) Individually-Administered Measures, Grade 5 Sample, Student Copies; and (15) Group-Administered Measures, Grade 5 Sample.