This paper investigates what has traditionally been viewed as syntactic acquisition, with the goal of questioning whether what appears to be syntactic acquisition is more appropriately described as lexical or semantic acquisition. Data come from responses to a grammaticality judgment test by learners of English as a second language at two proficiency levels. Four syntactic structures were examined. The sentences tested varied in the verbs used (e.g., John donated/gave Mary a present; John donated/gave a present to Mary). The results suggest that less proficient subjects use syntactic strategies, more proficient learners use more semantic based strategies, and there is more lexical differentiation at the lower levels of proficiency. Thus, as learners gain in proficiency, there is an increased influence of the semantic relatedness of lexical items.