OBJECTIVE. Sodium hydroxide matricectomy is a successful method for the treatment of ingrown toenails. This study was designed to evaluate the optimal sodium hydroxide application period providing high success rates with minimal postoperative morbidity.MATERIALS AND METHODS. Sixty-six patients with 225 ingrown nail edges were treated in three groups receiving 30-second, 1-minute, and 2-minute applications of sodium hydroxide. Each patient was reviewed postoperatively for pain, drainage, and tissue damage. The median long-term follow-up period was 14 months.RESULTS. The success rate of the therapy was 70.9% in the first group, 92.7% in the second group, and 94.4% in the third group. In all groups, about half of the patients experienced minimal pain within 48 hours following the operation, but only in the third group, 20% of the patients had minimal pain, which continued about 1 week. Drainage and tissue damage were minimal or mild in all groups and disappeared within 3 weeks in the first and second groups but were prolonged to 6 weeks in the third group.CONCLUSION. The success rate of 30-second application is significantly lower than 1-minute and 2-minute applications. Although the success rates of the latter two procedures are similar, the prolonged healing time is the disadvantage of the 2-minute application. We conclude that 1-minute application of 10% sodium hydroxide is simple, safe, and highly effective for the treatment of ingrown nails.