The study explored the contribution of prior knowledge and reliance on L1 syntactic knowledge to L2 written sentence comprehension. Participants, 102 native Hebrew speakers at three education levels (junior high, high school, and postsecondary), answered questions in two sentence categories: Semantically plausible sentences that readers can understand by linking their content words to prior knowledge; semantically neutral sentences, whose comprehension requires adequate syntactic processing. To track the benefits of linguistic transfer from Hebrew (L1) to English (L2), the study manipulated the languages' cross-linguistic structural similarity. The results suggest that Hebrew-speaking students rely on prior knowledge and/or on structural similarities between Hebrew and English to interpret English sentences. When they cannot rely on either of these two factors, they manifest remarkably poor understanding of quite basic English constructions even at the postsecondary level.