In the present work, the Authors studied the incidence of aflatoxin in 30 samples of peanut butter, (Arachis hypogaea, L.) beeing 10 from a Brazilian factory (A), 10 from another Brazilian factory (B) and 10 of 7 brands from U.S.A. The extraction of aflatoxin was made with chloroform, separated by thin-layer chromatography with Silicagel-G and quantified under an ultra-violet lamp. The results showed that only 3 samples (10%) were free from aflatoxin and were of U.S. origin; 6 (20%) had them under 0,05 ppm; 15 (50%) were between 0,05 and 0,25 ppm; 5 (16,6%) between 0,25 and 1,00 ppm. and 1 (3,3%) more than 1,00 ppm. These values express the total toxicity in terms of B1. The Authors have concluded that of the Brazilian samples, only 3 were in a condition for beeing consumed, and those still with some restrictions. They pointed out that one sample of the Factory B, have showed a very high level of aflatoxin.