Flocculation is prerequisite for bulk sedimentation of yeast during brewery fermentation. Although single yeast cells gradually sediment in green beer, this sedimentation rate is too slow without formation of large yeast flocs. Flocculation characteristics of yeast are strongly strain-dependent. In addition to the genetic background, several environmental factors affect flocculation. The review of Virve Vidgren and John Londesborough concerns the major determinants of yeast flocculation and sedimentation in brewery fermentations.