There has been many investigations on phytoagglutinin and especially, Moon et al reported a number of research works on phytoagglutinins prepared from the Korean plants. The present report describes results of experiment on the biological effect of 14 Korean phytoagglutinins to microorganism for the first time. 1) Kaolin rubi and Ricinus communis L. among 14 different species of Korean phytoagglutinins had agglutinating activities to microoganisms. 2) Kaolin rubi agglutinated E. coli, Staph. aureus, Ps. aeruginosa, Prot. vulgaris, B. subtilis, Sal. typhi, Sh. dysenteriae, C. albicans and Sa. cerevisiae but Ricinus communis L. showed only agglutination of Sa. cerevisiae. 3) Agglutinating titers of Kaolin rubi to various microorganisms were 500-1,000 but titer of Ricinus communis L. was only 50. 4) Ricinus communis L. showed bactericidal action to Sa. cerevisiae but Kaolin rubi had no such effect.