A rapid method is presented for determining free fatty acids in vegetable oils. The method utilizes the reaction of fatty acids with cupric acetate to form salts whose blue color in benzene solution may be measured colorimetrically. When 65 samples of crude soybean oil were tested by this colorimetric method and the results compared with the results of titration with standard alkali, the correlation was 0.992 with a standard deviation of 0.08% free fatty acid (F.F.A.).