This paper reports for the first time in smoked foods the presence of three tetrahydro‐ß‐carboline carboxylic acids. One of these, 1‐hydroxymethyl‐tetrahydro‐ß‐carboline‐3‐carboxylic acid, which is derived from the interaction of tryptophan and glycolaldehyde, and which has not previously been reported in foods, was observed in 20 samples at levels up to 444 μg/kg. The corresponding products which are derived from tryptophan and formaldehyde or tryptophan and acetaldehyde were found respectively in 28 samples at levels up to 22 mg/kg and in 16 samples at levels up to 881 μg/kg. Greater concentrations were generally found in those smoked foods having a lower pH value and produced by using a longer fermentation or maturation. Only l‐methyl‐tetrahydro‐ß‐carboline carboxylic acid (156–574 μg/kg) was found in the four unsmoked samples analysed.