The present research examines the nature of the different processes that have been proposed to underlie semantic priming. Specifically, it has been argued that priming arises as a result of automatic target activation and/or the use of strategies like prospective expectancy generation and retrospective semantic matching. This article investigates the extent that these processes rely on cognitive resources by experimentally manipulating working memory load. To disentangle prospective and retrospective processes, prime-target pairs were selected such that they were symmetrically associated (e.g., answer-question; SYM) or asymmetrically associated in either the forward direction (e.g., panda-bear; FA) or the backward direction (e.g., ball-catch; BA). The results showed that priming for FA pairs completely evaporated under a high working memory load but that it remained stable for BA and SYM pairs. This was taken to mean that prospective processes, which are assumed to cause FA priming, require cognitive resources, whereas retrospective processes, which lead to BA priming, are relatively effortless.