Purpose This study examines the developmental interplay between silent reading fluency and reading comprehension from Grade 1 to Grade 9 (age 7 to 15) in a large Finnish sample (N = 2,518). Of particular interest was whether the associations are bidirectional or unidirectional.

Methods Children’s silent reading fluency and reading comprehension skills were assessed using group-administered tests, at seven time points, in Grades 1, 2, 3, 4, 6, 7, and 9. A random intercept cross-lagged panel model with latent factors was used to identify between- and within-person associations between silent reading fluency and reading comprehension. The use of latent factors allowed for the controlling of measurement error.

Results The model showed that silent reading fluency and reading comprehension correlated at the between-person level, indicating that those who were proficient in one reading skill were typically good at the other also. At the within-person level, however, only some developmental associations emerged: in the early reading acquisition phase (Grade 1–2), silent reading fluency predicted reading comprehension, and in adolescence, reading comprehension weakly predicted silent reading fluency (Grade 7–9).

Conclusions The results thus suggest only weak developmental within-person associations between silent reading fluency and comprehension, although some unidirectional associations emerged with a change in the direction of the associations over time.