This study investigated the effect of: (1) direct written corrective feedback (WCF); and (2) opportunities for revision on the development of second language learners' explicit and implicit L2 knowledge in an EFL setting. Twenty-six intermediate-level university students were randomly divided into three groups: two treatment groups (direct feedback, direct feedback + revision), and a control group (no feedback). In a pretest-posttest design, over the span of six weeks, participants completed picture-prompted writing tasks, timed grammaticality judgment tests and error correction tests. Participants also produced two new writings with members of the direct feedback + revision group being given an opportunity to revise their writing. The results for the direct feedback group indicated accuracy gains in posttests. There was also some evidence that these gains were dependent on the structure targeted. However, there was no comparable improvement in the direct feedback + revision group. Therefore, it was not possible to interpret these effects as strong evidence for development of learners' L2 knowledge. Conversely, there was evidence that the direct feedback + revision group had benefitted from the opportunity to revise their writing.