Pectin had a flocculating activity and its flocculating activities in various suspensions were investigated. Flocculating activity of pectin in a kaolin suspension was markedly Stimulated by the addition of Al3+ and Fe3+ to the suspension. Optimum temperature for flocculating activity of pectin in the kaolin suspension was around 30 degreesC and high flocculating activity was obtained when 30 mg/l of pectin and 0.2 nM Fe3+ were added to the suspension. Other inorganic suspensions of activated carbon and acid clay were flocculated by pectin in the presence of Al3+ or Fe3+. Flocculation of organic suspensions such as cellulose and yeast by pectin occurred when 0.1 0.2 mM Fe3+ was present in the suspensions.