The effectiveness of commonly used procedures to correct trachomatous trichiasis of the upper lid was examined in a clinical trial in Oman. Lids were graded as having minor trichiasis (five or fewer lashes), major trichiasis (more than five lashes), and defective lid closure. Randomly allocated surgery specific for lid grade was completed in 384 lids, of which 369 (96%) were followed up once or twice approximately 9 and 21 months after surgery. The definition of operative success included no evidence of trichiasis and complete lid closure. Tarsal rotation was the most effective operation and was successful in 80% of cases of minor trichiasis, compared with success rates of 29% for electrolysis and 18% for cryoablation. Tarsal rotation was successful in 77% of cases of major trichiasis, compared with a 41% success rate for tarsal advance and rotation. Surgery for major trichiasis produced a significant improvement in visual acuity in operated vs nonoperated fellow eyes in a regression model incorporating the between-eyes correlation of visual acuity.