The call for longitudinal evidence on the efficacy of written corrective feedback (WCF) for ESL (English as a second language) writers has been made repeatedly since Truscott (1996) claimed that it is ineffective, harmful, and should therefore be abandoned. This article discusses some of the theoretical issues raised against the practice, outlines the status of recent empirical evidence and presents a 10-month study of the effects of WCF on two functional uses of the English article system given to 52 low-intermediate ESL students in Auckland, New Zealand. Assigned to four groups (direct corrective feedback, written, and oral meta-linguistic explanation; direct corrective feedback and written meta-linguistic explanation; direct corrective feedback only; the control group), the students produced five pieces of writing (pre-test, immediate post-test, and three delayed post-tests). Each of the treatment groups outperformed the control group on all post-tests and no difference in effectiveness was found between the three treatment groups.