Summary.1. Eating and drinking behaviour have been studied in mice made obese by injection of goldthioglucose.2. Continuous recordings of food and water intake showed that the obese mice ate less frequently but much larger average amounts of food compared to the control animals.3. It is suggested that because of damage to structures in the ventro‐medial parts of the hypothalamus in the obese mice, these animals are more dependent on the peripheral mechanisms regulating food intake, such as that referable to the gastrointestinal tract.4. The obese mice were not able to compensate with increased food intake when kaolin as caloric inert material was added to the diet.5. The control animals compensated for kaolin added to the diet by increasing the meal frequency or the amount of food eaten each time or by a combination of both.6. The obese mice showed little ability to increase their food intake when forced to exercise or when exhibiting a progressively increasing “spontaneous” activity.7. Continuous recordings of water consumption showed that no damage to the mechanisms regulating water intake was incurred in this type of ob