OBJECTIVE To determine the current prevalence of simple goitre in the school population of a health district where goitre is traditionally endemic. Calculation of the deficiency or otherwise of iodine through the determination of mean urinary excretion of iodine in the population under study. METHODS Cross-sectional descriptive study. METHODS Olvera Health District (Cádiz). METHODS School students in the health district between 6 and 14 years old out of a total of 1969. Sample size of 92 school students was chosen at random, for a 95% confidence interval. RESULTS Dependent variables were the existence of goitre found in a physical examination, urinary excretion of iodine measured in microg/dl in the first urine of the morning, origin of water consumed and habitual consumption of iodised salt in their diet. 87% of the population under study habitually drank water from the normal supply, 4% from wells or springs, and 9% mineral water. 57% of parents did not know whether the salt in their normal diet was iodised or not. 29.3% of school students included in the study had some degree of goitre. The mean excretion of iodine in urine was 13.78 microg/dl (95% CI, 12.30-15.26). Ioduria was below 9.9 microg/dl in 28.2%, within the endemic figures. CONCLUSIONS The mean amount of iodine in urinary excretion in the sample means that the risk of developing goitre is low, although the prevalence of goitre continues at endemic figures.