—A mass fragmentographic method for the assay of phenylethylamine (PEA) and a number of related amines in several biological materials is described. The gas chromatographic column employed for this analysis is a 12ft 1/8 in. o.d. steel column packed with 0.5% OV22+ 2% SE54 + 1% OV210 coated on 80/100 mesh chromosorb W (HP). The mass spectral characteristics of these amines are illustrated, compared, and discussed. Of the various monoamines which could be measured, only PEA, m‐ and p‐tyramine were detected in measurable quantities. Phenylethanolamine and p‐octopamine were found in trace amounts in urine, plasma, cerebrosponal fluid, and rat brain. No diurnal variation in the urinary excretion of PEA, m‐ and p‐tyramine was observed. Plasma concentration of PEA or p‐tyramine did not significantly change 1 h after eating a breakfast. Furthermore, consuming 200 g of Cadbury milk chocolate containing about 1 mg of PEA, 0.1 mg of phenylethanolamine and 10 mg of p‐tyramine did not significantly alter urine excretions of these three amines. In the brain, as has been reported by others, we found that PEA and p‐tyramine are not evenly distributed and that the highest concentrations are found in the hypothalamus and caudate. From the results obtained we concluded that PEA, m‐ and p‐tyramine are probably produced from endogenous sources and that the direct contribution of diet to their urine excretion is small. Copyright © 1979, Wiley Blackwell. All rights reserved