1. Body weight was measured through forty consecutive illnesses in seventeen patients with oedema in association with chronic bronchitis and hypoxia. All patients were taking diuretic drugs at the time.
2. Body weight increased little as peripheral oedema and a raised jugular venous pressure appeared. The subsequent weight-loss during treatment was usually greater than the pre-treatment weight-gain. Body weight increased slowly in convalescence to equal or exceed hospital admission weight without a deterioration of general health or reappearance of oedema.
3. Total body water, exchangeable sodium and exchangeable potassium were measured in patients after treatment of the acute illness and clearance of oedema and again in six patients of the group 2–3 months later in convalescence. Total exchangeable sodium was normal or slightly reduced after treatment of oedema and in convalescence between recurrent acute illnesses. Even when gross oedema was present exchangeable sodium was substantially increased in only one of three patients studied at this stage. Total exchangeable potassium was invariably severely depressed.
4. Large changes of body tissue weight without comparable change in exchangeable sodium support previous evidence that oedema in hypoxic bronchitis is not simply a further form of congestive cardiac failure.
5. It is suggested that at least some of the tissue loss in acute exacerbations is a direct result of hypoxaemia and similar to that observed at high altitude. Part of the oedema fluid is thought to be derived from intracellular water released during dissolution of tissue matrix.