['Clinically, constant severe trachoma predicts an increased risk of scarring in children. There are no data on the risk of scarring associated with constant infection with Chlamydia trachomatis, regardless of clinical manifestation. We propose to determine the 5-year incidence of scarring in children with a history of constant severe trachoma, constant infection, or both compared with children who had a history of neither.', 'A 5-year, longitudinal observational study.', 'Children aged less than 10 years with data on trachoma and infection for 3 of the 5 visits in the first 18 months, and follow-up 5-year data on scarring.', 'Data were collected on clinical trachoma, and ocular swabs were taken to determine the presence of C. trachomatis in children in a hyperendemic village in Tanzania. Images were graded for scarring. Data were collected at baseline; 2, 6, 12, and 18 months; and 5 years from baseline. Severe trachoma was defined as the presence of 10 or more follicles, or trachoma intense. A child had constant infection (severe trachoma) if infection (severe trachoma) was present on at least 3 visits before the 5-year survey.', 'Five-year risk of scarring.', 'Of the 189 children, 22 (11.6%) had constant severe trachoma, but not constant infection. Nine children (4.8%) had constant infection but not constant severe trachoma. Both constant severe trachoma and constant infection were present in 16 children (8.5%). The 5-year incidence of scarring was similar in all 3 groups; children with constant severe trachoma only, with constant infection only, and with both were most likely to develop scars (35.0%, 44.4%, 31.2%, respectively) compared with those with sporadic trachoma or infection (15.2%) or neither (6.8%) (P = 0.0002).'] Does constant ocular infection with Chlamydia trachomatis predict risk of scarring in children in Tanzania?