In the componential approach to modelling reading ability, a number of contributory factors have been empirically validated. However, research on their relative contribution to explaining performance on second language reading tests is limited. Furthermore, the contribution of knowledge of syntax has been largely ignored in comparison with the attention focused on vocabulary. This study examines the relative contribution of knowledge of syntax and knowledge of vocabulary to L2 reading in two pilot studies in different contexts--a heterogeneous population studying at the tertiary level in the UK and a homogenous undergraduate group in Japan--followed by a larger main study, again involving a homogeneous Japanese undergraduate population. In contrast with previous findings in the literature, all three studies offer support for the relative superiority of syntactic knowledge over vocabulary knowledge in predicting performance on a text reading comprehension test. A case is made for the robustness of structural equation modelling compared to conventional regression in accounting for the differential reliabilities of scores on the measures employed. (Contains 1 figure, 8 tables and 5 footnotes.)