Polyacrylamide gel electrophoresis was used to study B-esterases (EC 3.1.1.1) and C-esterases (EC 3.1.1.6) in five species of Collembola--; Folsomia candida, Proisotoma vesiculata, H,ypogastrura denticulata, and two undescribed species of Isotoma,. Ef values were computed for zymograms of 105 individuals and compared both within and among species. Certain bands-three to six in number--predominated on the zymograms of each species. The predominating bands differed among the five species resulting in a unique zymogram for each.It was also found that zymograms of normal and ecomorphic forms of Proisotoma vesiculata were dissimilar. Zymograms of specimens of Folsomia candida with access to food and those without food for 48 and 72 hours were similar. Zymograms from mascerated specimens frozen in buffer were not satisfactory.