With a constant microinfusion technique for administration of palmitate-1-¹⁴C, a FFA flux rate of 286–654μEq./min. (average 533) was found in 5 control subjects as against a flux rate of 663–959 μEq./min. (average 837) in 5 untreated obese patients. When expressed per kilogram lean body mass (LBM) (obtained by whole body counting of ⁴⁰K) the FFA flux rate was considerably higher in the obese people (16.98–24.78 μEq./min. Kg. LBM, average 20.49) than in the controls (9.17–14.31, average 11.55). Treatment by intermittent starvation did not directly affect this high rate of lipolysis. 1.5 months after having reached a normal body weight, one patient, treated by calorie-restriction only, exhibited normalization of the previously high FFA turnover rate. A comparative study of the mentioned parameters was made in 2 patients with a pheochromocytoma (with a high lipolysis rate, corrected after operation) and 1 patient suffering from anorexia nervosa (with a depleted body fat mass). It is considered probable that in the pathogenesis of human “exogenous” obesity, impairment of lipolysis is not primarily involved. The plasma triglyceride influx rate in the obese patients was high as compared to that in the controls, when expressed as μmole/min./L.plasma. This high rate of esterification, too, showed no diminishment shortly after starvation treatment.