A kairomone from white mustard, Sinapis alba , that attracts infective juveniles (J2) of the beet cyst nematode, Heterodera schachtii, was extracted from root exudates and enriched by rotary evaporation. The kairomone-containing root exudate fractions were then repeatedly enriched and separated on a combination of octyl and octadecyl columns, leaving a single UV-absorbing HPLC peak. Glucose and fructose were identified by a subsequent HPLC separation in the ion moderated partition chromatography mode. The kairomone appeared in the fructose-containing fraction. As fructose did not cause nematode attraction, the fructose fraction contained at least one further substance. HPLC separations showed that the kairomone shares several properties with fructose and that it is relatively more polar than those compounds giving an UV signal. The repeated reversed-phase and ion moderated partition chromatography separations of single kairomone-containing fractions indicate that the kairomone is composed of one single substance which could not be identified with the methods applied. Gas chromatographic and mass spectrometric analyses revealed the presence of glucose, fructose, myo-inositol, sucrose and xylofuranose/ribofuranose in S. alba root exudates.