Tuberculosis in children provides essential epidemiological information because it always indicates recent transmission. It is therefore important to have effective epidemiological surveillance of childhood tuberculosis. This study was conducted to describe the characteristics of children receiving treatment for tuberculosis infection or disease in order to define a reporting criterion appropriate for children and to estimate the incidence of Mycobacterium tuberculosis infection in children in a high-incidence region. The study included children under 15 years of age who were placed on antituberculosis treatment for tuberculosis infection or active tuberculosis in public hospitals in the Île-de-France region between January 1 and December 31, 1997. Sociodemographic and clinical data were collected using a standardized questionnaire. Thirty-nine (93%) of the 42 hospitals contacted participated in the study. Among the 240 children included, 73 (30%) had active tuberculosis and 167 (70%) had latent tuberculosis infection. Fifty percent of the children were under 6 years of age. The country of birth was France for 163 (76%) children and abroad for 51 (24%), but 80% of the children had parents born abroad. The diagnosis was made as part of a routine examination unrelated to any diagnosed tuberculosis case in the child’s social circle for 106 (45%) children, as part of screening among contacts of a tuberculosis case for 92 (39%) children, and for 36 (16%), clinical signs had led the child to seek medical care. One hundred ninety-seven (86%) children had received at least one BCG vaccination. For 36 of the 73 (49%) children with active tuberculosis, the disease was pulmonary. It was extrapulmonary in 10 (14%) children. Two children had tuberculous meningitis and two had a disseminated form of the disease. The bacteriological specimen was positive on microscopic examination in 10 (14%) children and the culture was positive in 25 (34%) children. The probable source of infection was known for 102 (52%) children. The incidence rate of active TB in the Ile-de-France region found by the survey was 3.3 per 100,000 children under 15 years of age in 1997, whereas the incidence rate in -France, calculated from mandatory reporting (MR) data, was 7.5 per 100,000 children under 15 years of age, more than twice that of the survey. Despite the imperfect completeness of our study in identifying cases, 56% of MR reports in Paris corresponded to infections. It is therefore difficult to quantitatively assess the prevalence of childhood tuberculosis in France based on the reporting system. This study provided a better understanding of the epidemiological characteristics of childhood tuberculosis in the Ile-de-France region, highlighted the specific challenges of monitoring childhood tuberculosis, and revealed the limitations of the current mandatory reporting system. The study’s steering committee recommended mandatory reporting of tuberculosis infection in children, as infection is a sensitive indicator of transmission and of how the disease is being controlled in the population. Knowledge of infection cases by the services responsible for tuberculosis control will enable the early implementation of necessary actions to identify the source of infection and other secondary cases. (R.A.)