The extraction of a lectinic factor involved in yeast flocculation, from two Kluyveromyces lactis strains (a flocculent K. lactis 5c and a non-flocculent K. lactis 5a strain) was performed using EDTA and two surfactants, Hecameg and HTAC. The properties of the different extracts were tested by haemagglutination and reflocculation of deflocculated K. lactis 5c cells. Hecameg gave the highest yields of active lectinic extract but the extraction with EDTA seemed more specific. HTAC extracts showed a very low activity. The possibilities of extraction of the agglutinating factor, either by an ion chelator or by surfactants, suggest that this factor may be anchored in the cell envelope, i.e. the cell wall and the membrane, by different mechanisms. All the assays revealed a galactose-specific lectinic activity was present that in the flocculent as well as in the non-flocculent strain. This indicates that the absence of flocculation with K. lactis 5a is mainly due to a defect in the ligands of the lectin rather than to a loss of the lectinic factor itself.