A low-cost biochemistry experiment is described that demonstrates current techniques in the use of catalytic DNA molecules and introduces a nonradioactive, nonfluorescent, inexpensive, fast, and safe method for monitoring these nucleic acid reactions. The laboratory involves the exploration of the 10-23 DNA enzyme as it cleaves a specific RNA substrate, and the reaction is visualized qualitatively following gel electrophoresis. This experiment provides the students with hands-on experience manipulating nucleic acids using polyacrylamide gel electrophoresis to visually follow the kinetics of the reaction and introduces the student to a novel postelectrophoretic stain, cresyl violet, for detection of the nucleic acids. These DNA enzyme catalysts have potential applications in both biotechnology and medicine and therefore should be of great interest to upper-level undergraduate students. (Contains 4 figures.)