A study has been made of an iodine-deficient population living in an extended village in the Karakoram Himalayas. There is evidence that the incidence of goitre increases towards the lowest part of the village, in accordance with the findings of McCarrison, who worked in the same region in the early years of the twentieth century. McCarrison ascribed the variation of goitre incidence to increasing pollution of drinking water as it travelled downstream, and postulated a bacteriological goitrogenic factor. However, the observations reported here show no correlation between goitre incidence and the bacterial concentration of drinking water, nor are there iodine-metabolizing micro-organisms present in the water. It may be that a differential iodine deficiency throughout the village can account for the variation in goitre incidence, since the soil can adsorb appreciable amounts of radio-iodine. The indices of thyroid function show that all the inhabitants are exceptionally iodine-deficient, although most of them are clinically euthyroid. As well as having a greatly enhanced mean thyroid iodide clearance the population has a mean renal iodide clearance which is lower than normal. Intra-muscular injections of iodized oil were acceptable to the villagers, and 477 injections were administered. Fingerprints and palm prints were collected from a sample of the population, yielding a pattern distribution comparable with other populations in the Indian subcontinent. The ratio of PTC tasters to non-tasters among the inhabitants is not significantly different from the ratio found in Europe.