A mixture of six new long chain ketodienes, (6Z,26Z)-pentatriacontadien-2-one [1], (8Z,26Z)-pentatriacontadien-2-one [2], (6Z,27Z)-hexatriacontadien-2-one [3], (8Z,27Z)-hexatriacontadien-2-one [4], (6Z,28Z)-heptatriacontadien-2-one [5], and (8Z,28Z)-heptatriacontadien-2-one [6], has been separated from the cuticular lipids of the Guam brown tree snake Boiga irregularis. Their structures were determined by chemical and spectral means.