This study investigated slope bias on student background variables for both Curriculum Based Measurement of Oral Reading (CBM-R) and Curriculum Based Measurement Maze Reading (Maze). Benchmark scores from 1,738 students in Grades 3 through 8 were used to examine potential slope bias in CBM-R and Maze. Latent growth modeling was used to both estimate growth rates and examine the extent to which demographic variables affected the estimated growth rates. Results indicate a significant CBM-R slope bias on special education status at Grade 3 and on gender at Grade 7. For Maze, slope bias on gender was associated with Maze slope estimates at Grades 5 and 7. Slope bias on various demographic variables was not consistent across CBM measures and grades. Results and implications are discussed. (Contains 1 figure and 4 tables.)