Alpha-amino acids were pyrolysed at 600 degrees C in the presence of hexamethyldisilazane (HMDS) and the formed volatile products were analysed on line by gas chromatography-mass spectrometry (GC-MS). Glycine, alanine, valine, leucine, isoleucine, norleucine, methionine, phenylalanine yielded principally the trimethylsilyl (TMS) ester of the parent amino acid. TMS esters of carboxylic acids arising from reductive deamination were observed for serine, threonine and aspartic acid. Decarboxylation resulted in the formation of amines which represented abundant products released from tyrosine, cysteine and methionine. Cyclic compounds arising from the condensation of two amino acids were revealed as characteristic products of glycine, alanine, serine, proline and hydroxyproline. Degradation products of the side chain were released at relatively high levels from tryptophane, tyrosine and hystidine. Since each amino acid produced a characteristic distribution of TMS products, in-situ pyrolysis/silylation with HMDS may find application as a screening technique for the detection of amino acids and related materials in complex matrices. The potentiality of the procedure was tested on a dipeptide (Tyr-Leu).