1. The metabolism of palmitic acid (a saturated fatty acid) and linoleic acid (a polyunsaturated fatty acid) was compared in seven subjects during constant infusions of the radioactive tracers.
2. The studies were repeated in some subjects after the turnover of the free fatty acids and the size of the fatty acid and glyceride pools had been altered with sucrose or polyunsaturated fat diets.
3. The fractional turnover of linoleic acid was nearly always greater than that of palmitic acid, though its total turnover rate was less.
4. A lesser proportion of the turnover of linoleate than of palmitate was incorporated into plasma triglyceride over a range of turnover rates of free fatty acids and glyceride fatty acid pools. This may be a factor in the lowering of plasma triglyceride concentrations with diets rich in polyunsaturated fatty acids.