Summary A method for separating tyramine from tyrosine and for estimating the concentration of the former substance was applied to cheese. This method involved the use of a continuous ether extractor and the employment of the Millon reagent using a colorimeter. Twenty-five samples of commercial American Cheddar cheese of different age and history were tested for tyramine. All were found to contain tyramine in varying degrees of concentration. The average for these samples was 384 γ per g. or 0.0384 per cent; the highest concentration was 1,199 γ per g. or 0.1199 per cent, and the lowest was 25 γ per g., or 0.0025 per cent. A large number of miscellaneous varieties of ripened types of commercial cheese were tested for tyramine. Again, all samples were found to contain tyramine in varying concentrations. The largest amount was found in a Liederkrantz cheese which had a concentration of 1,683 γ per g., or 0.1683 per cent, while the smallest amount was found in a Roquefort cheese with a concentration of 48 γ per g. or 0.0048 per cent. The analyses were not sufficiently extensive to establish differences due to cheese variety. Tyramine was isolated from a sample of Cheddar cheese by this method, purified, and identified as the dibenzoyl derivative.