The effect of coffee, decaffeinated coffee and a control beverage on plasma FFA was studied in a group of normal human subjects. The effect of caffeine sodium benzoate was also studied in the dog. Significant elevations in FFA were observed after coffee and caffeine which usually reached their peak in 3 or 4 hours. The administration of sucrose significantly reduced the immediate FFA response. The FFA effects with decaffeinated coffee were markedly less than with regular coffee and were similar to that of the control beverage. These effects are considered to be of importance, particularly in that they may be related to other disturbances in lipid metabolism. © 1968.