The thermal behaviour of argentilactone 1 has been studied by the use of flash vacuum pyrolysis (FVP) techniques. The E- and Z-isomers of 2-octenal 7 were found to be the major non-gaseous products of the thermal ring-opening of argentilactone at 650-850 degrees C; no undecatrienes 2-6 could be identified in the pyrolysate mixtures. (c) 2007 Elsevier B.V. All rights reserved.