Repeated reading (RR) is often recommended for promoting reading fluency, but it is unclear whether continuous texts or word lists should be used. This study tested whether the effects of RR depend on the reading material and whether these effects interact with students' prior abilities. N = 304 primary school students were randomly assigned to one of three conditions: (1) a repeated reading group receiving continuous texts (RR-T), (2) a repeated reading group receiving word lists (RR-W), and (3) a control group (CG). Before and after the training (M = 13 sessions), students' reading fluency and reading motivation were assessed. In both RR-groups, the average level and growth in (a) words read correctly per minute and (b) affect were recorded during each reading session. Multilevel modelling revealed that growth in reading fluency and reading motivation did not differ significantly between the RR groups and the CG. Process analyses showed that the number of words students read correctly per minute increased significantly per session. Students' affect remained stable at a high level throughout the reading interventions. In the RR-T, significantly more words were read correctly than in the RR-W, and this was a mediator between group and reading fluency. Students' initial levels of reading performance and reading motivation strongly predicted both process and outcome variables, but not in interaction with the reading material. Results emphasise the importance of investigating the effects of repeated reading interventions with higher dosage and of offering differentiated methods (instead of reading material) to struggling readers.