BACKGROUND Iodine deficiency disorders (IDDs) are an important cause of mental handicap and poor educability of children. Though Delhi does not lie in the classical Himalayan goitre belt, it has been shown that IDD was endemic in Delhi. Studies of school children in Delhi reported a total goitre rate of 55% which indicates severe endemicity. The sale of uniodized salt has been banned in Delhi since July 1989. This study was done five years later to assess the impact of this measure on IDD prevalence in Delhi. METHODS A cross-sectional study was done among class VI students studying in government schools of Delhi. A complete list of government middle schools in Delhi was obtained and 30 were selected on the basis of 'probability proportion to size'. A sample size of 1200 was decided based on an expected prevalence of 50% with 5% error and design effect of three. All children in class VI of each school were clinically examined by a trained doctor for the presence of goitre and casual urine samples were collected in capped plastic tubes. The urinary iodine estimation was done by the wet ashing method. RESULTS The total goitre rate was 20.5%. If the results were limited to children in the age group of 10-12 years it was 19.7%. The urinary iodine was less than the recommended 100 micrograms/L of urine in 23.6% of the children; 7.6% had no iodine in the urine. It is possible that some children could have substituted water in place of urine. The median urinary iodine level was 198 micrograms/L of urine. CONCLUSION The study showed that IDD continues to be prevalent in mild endemic proportions. Compared to the results of previous surveys, the IDD rates have declined in the last few years. However, it continues to be an important public health problem in Delhi. It is essential to monitor the iodine content of salt on a regular basis. IDD control activities should be strengthened in Delhi and repeat surveys should be done every 3-5 years to monitor the progress achieved in eliminating IDD.