ABSTRACTA large proportion of vocabulary is acquired incidentally from written contexts However, in text-based studies promoting generative processing,it is not dear if, or to what extent, generation influences incidental vocabulary learning This study examined the effects of text-based tasks and background knowledge (pnor vocabulary knowledge and a disposition to use generative learning tactics when takling new vocabulary) on incidental vocabulary acquisition Forty-eight adult ESL learners were randomly assigned to one of three treatments (a) reading and retelling a text with explicit generative training and without access to the text during recall, (b) reading and retelling a text without explict generative training but with access to the text during recall, and (c) neither reading nor retelling a text All subjects sat a pre-test (individual interviews and a read and retell task) and post-tests (individual interviews and two multiple-choice tests) designed to tap partial vocabulary knowledge gains Results indicated that the process of reading and retelling a text promotes incidental vocabulary learning and that generative processing enhances vocabulary learning with greater levels of generative processing leading to greater vocabulary gains for unknown words