Previous research investigating the effects of unassisted and assisted repeated reading has primarily focused on how each approach may contribute to improvement in reading comprehension and fluency. Incidental learning of the form and meaning of unknown or partially known words encountered through assisted and unassisted repeated reading has yet to be examined in an ecologically valid context. This study investigated the effects of assisted and unassisted repeated reading on incidental vocabulary learning with beginner readers over two seven-week periods. A total of 82 students who were 15-16 years old and studying English as a foreign language in Taiwan read or read and listened to 28 short texts several times. To measure the effects of each condition, a modified vocabulary-knowledge scale was used in a pre-test and post-test design. The results indicated that both types of repeated reading contributed to vocabulary learning with assisted repeated reading leading to significantly greater vocabulary knowledge. The implications for the development of reading skills and vocabulary size are discussed in detail. (Contains 2 notes, 5 tables, and 2 figures.)