The essential oil of NEPETA NEPETELLA L. growing in the Aosta Valley (Valnontey), Italy, obtained by steam distillation of the leaves and the flowers, was investigated by capillary gas chromatography in combination with mass spectrometry. To facilitate identification, fractionation of the oil with straight phase HPLC was performed. Nepetalactone (76.5%) is the main component of the oil. The isomers epinepetalactone (0.6%) and neonepetalactone (0.4%) together with the dihydro (1.6%) and dehydro (traces) nepetalactone derivatives were also identified. These compounds are considered to be responsible for the feline attractant activity of NEPETA NEPETELLA L.