Trabeculectomy was performed on 14 consecutive phakic eyes, and measurements of axial anterior chamber depth were taken preoperatively and on postoperative days 1, 2, 3, 6 and 14. The mean maximal change in anterior chamber depth occurred on the 1st postoperative day, while the anterior chamber reached its shallowest state on the 2nd postoperative day. No significant change in mean anterior chamber depth occurred on successive visits from postoperative day 1 through 14. The anterior chamber approached the preoperative level by postoperative day 14. Because reformation of anterior chamber after trabeculectomy takes about 2 weeks, close observation is essential when marked shallowing occurs early.