In the treatment of flexor tendon injury of the hand, re-rupture after primary tendon repair is one of complications which occurs occasionally and so impose burden on both the patient and the surgeon. Authors experienced twelve cases of re-rupture after primary flexor tendon repair of 274 patients from Mar. 1989 to Mar.1996. The incidence of re-rupture after primary flexor tendon repair was 4.4% in author's series. One case happened with slip down injury, and in six cases re-rupture occurred during physical therapy with snapping click sound. However in five cases, the patients conldnt recognize any related causes. In majority of cases, re-ruptures were identified between three and five weeks after primary repair by the surgeon and the patient, so it could be suggested that the attention should be paid for the high possiblity of re-rupture during this period. Operative findings were the resorption and friability of repaired end with insecure suture fixation in two cases, rupture of suture material in four cases and loosening of the knot in six cases. From this study, the authors suggest the importance of knot, and recommend to make more than four knots on suture tie with attention to the tie direction, and advise careful physical therapy according to each patients' different situation. In the treatment of re-rupture, end-to-end re-anastomosis was available in seven cases (59%). In five cases (41%), tendon graft was needed. The clinical result of the re-rupture cases was evaluated by the Stickland evaluation method, and it was satisfactory in 67% of the patients who had the complication of re-rupture.