Onychophorans use their adhesive secretion to capture prey and for defense. The protein composition of this secretion was studied in several species of Epiperipatus from Costa Rica, using polyacrylarnide gel electrophoresis with sodium dodecyl sulphate (SDS-PAGE). A complex pattern of proteins appeared in acquous extracts of the secrelion after electrophoresis and slaining with Coomassie Brilliant Blue. Many conserved high molecular weight bands are detected, and a few low molecular weight bands that are abundant and species-specific. Extracts from many different individuals of the abundant species E. biolleyi show identical patterns, while each of the four species analized had a unique band patíern. These specific patterns of small peptides may be useful for taxonomic identification in this phylum. The large variability in size and number of these peptides suggests Ihat they play a general function such as gelation through disulfide bond formation, and not a specific catalytic function