The essential oil of Scleria hirtella was obtained by hydrodistillation and analysed by GC and GCâMS. The major constituents were nonanal (42.0%), geranial (25.3%) and neral (15.3%). It is a remarkable essential oil presenting a series of aliphatic aldehydes between C-7 and C-15, where the C-9 derivative is the most prominent. The aldehydes were probably generated from the oxidation of polyunsaturated fatty acids by plant enzymes. Copyright © 2005 John Wiley & Sons, Ltd.