The paper first describes a web-based essay critiquing system developed by the authors using latent semantic analysis (LSA), an automatic text analysis technique, to provide students with immediate feedback on content and organisation for revision whenever there is an internet connection. It reports on its effectiveness in enhancing adult EFL students' writing quantitatively and qualitatively. Finally it suggests ways to use the system effectively. An experimental study was conducted. Twenty-seven student writers, who were assigned to the control and experimental groups randomly, wrote a 300-word argumentative essay, a genre usually tested in local and public examinations, over an 80-minute duration. The experimental group received two modes of feedback from the system whereas the control group typed and revised their essays on the computer in the traditional pen and paper way only. Their final submissions were co-marked by two raters, and comparison on essay length and final scores between the two groups was made. Although it was found that there was no statistically significant difference between the two groups in these two aspects, the experimental group's writing strategies shed some light on pedagogy. (Contains 5 tables, 3 figures and 11 notes.)